Noise, Vibration And Harshness (NVH)

Special Tool(s)

	ChassisEAR 107-R2102 or equivalent
	Vibration Analyzer 100-F027 (014-00344) or equivalent
	EngineEAR 107-R2100 or equivalent
	Ultrasonic Leak Detector 134-R0135 or equivalent

To assist the service advisor and the technician, a Write-up Job Aid and an NVH Diagnostic Guide are included with this material. The Write-up Job Aid serves as a place to record all important symptom information. NHV Diagnostic Guide serves as a place to record information reported on the Write-up Job Aid as well as data from the testing to be carried out.

To begin a successful diagnosis, fill out the NVH Diagnostic Guide, record the reported findings, then proceed to each of the numbered process steps to complete the diagnosis.

1: Customer Interview

The diagnostic process starts with the customer interview. The service advisor must obtain as much information as possible about the concern and take a test drive with the customer. There are many ways a customer will describe NVH concerns and this will help minimize confusion arising from descriptive language differences. It is important that the concern is correctly interpreted and the customer descriptions are recorded. During the interview, ask the following questions:

• When was the concern first noticed?
• Did the concern appear suddenly or gradually?
• Did any abnormal occurrence coincide with or proceed its appearance?

Use the information gained from the customer to accurately begin the diagnostic process.

2: Pre-Drive Check

It is important to do a pre-drive check before road testing the vehicle. A pre-drive check verifies that the vehicle is relatively safe to drive and eliminates any obvious faults on the vehicle.

The pre-drive check consists of a brief visual inspection. During this brief inspection, take note of anything that will compromise safety during the road test and make those repairs or adjustments before taking the vehicle on the road.

3: Preparing for the Road Test

Observe the following when preparing for the road test:

• Review the information recorded on the NVH Diagnostic Guide. It is important to know the specific concern the customer has with the vehicle.
• Do not be misled by the reported location of the noise or vibration. The cause can actually be some distance away, transferred from another part of the vehicle.
• Remember that the vibrating source component (originator) may only generate a small vibration. This small vibration can in turn cause a larger vibration or noise to emanate from another receiving component (reactor), due to contact with other components (transfer path).
• Conduct the road test on a quiet street where it is safe to duplicate the vibration or noise. The ideal testing route is an open, low-traffic area where it is possible to operate the vehicle at the speed in which the condition occurs.
• If possible, lower the radio antenna in order to minimize turbulence. Identify anything that could potentially make noise or be a source of wind noise. Inspect the vehicle for add-on items that create vibration/noise. Turn off the radio and the heating and cooling system blower.
• The engine speed is an important factor in arriving at a final conclusion. Therefore, connect an accurate tachometer to the engine, even if the vehicle has a tachometer. Use a tachometer that has clearly defined increments of less than 50 rpm. This ensures an exact engine speed reading.

4: Verify the Customer Concern

Verify the customer concern by carrying out a road test, an engine run-up test, or both.

The decision to carry out a road test, an engine run-up test, or both depends on the type of NVH concern. A road test may be necessary if the symptom relates to the suspension system or is sensitive to torque. A drive engine run-up (DERU) or a neutral engine run-up (NERU) test identifies noises and vibrations relating to engine and drivetrain rpm. Remember, a condition will not always be identifiable by carrying out these tests, however, they will eliminate many possibilities if carried out correctly.

5: Road Test

NOTE: It may be necessary to have the customer ride along or drive the vehicle to point out the concern. During the road test, take into consideration the customer's driving habits and the driving conditions. The customer's concern just may be an acceptable operating condition for that vehicle.

The following is a brief overview of each test in the order in which it appears. A review of this information helps to quickly identify the most appropriate process necessary to make a successful diagnosis. After reviewing this information, select and carry out the appropriate test(s), proceeding to the next step of this process.

• The Slow Acceleration Test is normally the first test to carry out when identifying an NVH concern, especially when a road test with the customer is not possible.
• The Heavy Acceleration Test helps to determine if the concern is torque-related.
• The Neutral Coast Down Speed Test helps to determine if the concern is vehicle speed-related.
• The Downshift Speed Test helps to determine if the concern is engine speed-related.
• The Steering Input Test helps to determine how the wheel bearings and other suspension components contribute to a vehicle speed-related concern.
• The Brake Test helps to identify vibrations or noise that are brake-related.
• The Road Test Over Bumps helps isolate a noise that occurs when driving over a rough or bumpy surface.
• The Engine Run-Up Tests consist of the Neutral Run-up Test and the Engine Load Test. These tests help to determine if the concern is engine speed-related.
• The Neutral Run-up Test is used as a follow-up test to the Downshift Speed Test when the concern occurs at idle.
• The Engine Load Test helps to identify vibration/noise sensitive to engine load or torque. It also helps to reproduce engine speed-related concerns that cannot be duplicated when carrying out the Neutral Run-up Test or the Neutral Coast Down Test.
• The Engine Accessory Test helps to locate faulty belts and accessories that cause engine speed-related concerns.
• The Vehicle Cold Soak Procedure helps to identify concerns occurring during initial start-up and when an extended time lapse occurs between vehicle usage.

Slow Acceleration Test

To carry out this test, proceed as follows:

• Slowly accelerate to the speed where the reported concern occurs. Note the vehicle speed, the engine rpm and, if possible, determine the vibration frequency.
• Attempt to identify from what part of the vehicle the concern is coming.
• Attempt to identify the source of the concern.
• Proceed as necessary.

Heavy Acceleration Test

To carry out this test, proceed as follows:

• Accelerate hard from 0-64 km/h (0-40 mph).
• Decelerate in a lower gear.
• The concern is torque-related if duplicated while carrying out this test.
• Proceed as necessary.

Neutral Coast Down Speed Test

To carry out this test, proceed as follows:

• Drive at a higher rate of speed than where the concern occurred when carrying out the Slow Acceleration Test.
• Place the transmission in NEUTRAL and coast down past the speed where the concern occurs.
• The concern is vehicle speed-related if duplicated while carrying out this test. This eliminates the engine and the torque converter as sources.
• If the concern was not duplicated while carrying out this test, carry out the Downshift Speed Test to verify if the concern is engine speed-related.
• Proceed as necessary.

Downshift Speed Test

To carry out this test, proceed as follows:

• Shift into a lower gear than the gear used when carrying out the Slow Acceleration Test.
• Drive at the engine rpm where the concern occurs.
• The concern is engine speed related if duplicated while carrying out this test. This eliminates the tires, wheels, brakes and the suspension components as sources.
• If necessary, repeat this test using other gears and NEUTRAL to verify the results.
• Proceed as necessary.

Steering Input Test

To carry out this test, proceed as follows:

• Drive at the speed where the concern occurs, while making sweeping turns in both directions.
• If the concern goes away or gets worse, the wheel bearings, hubs, U-joints (contained in the axles of 4WD applications), and tire tread wear are all possible sources.
• Proceed as necessary.

Brake Test

To carry out this test, proceed as follows:

• Warm the brakes by slowing the vehicle a few times from 80–32 km/h (50–20 mph) using light braking applications. At highway speeds of 89–97 km/h (50–60 mph), apply the brake using a light pedal force.
• Accelerate to 89–97 km/h (55–60 mph).
• Lightly apply the brakes and slow the vehicle to 30 km/h (20 mph).
• A brake vibration noise can be felt in the steering wheel, seat or brake pedal. A brake noise can be heard upon brake application and diminish when the brake is release.

Road Test Over Bumps

To carry out this test, proceed as follows:

• Drive the vehicle over a bump or rough surface one wheel at a time to determine if the noise is coming from the front or the back and the left or the right side of the vehicle.
• Proceed as necessary.

Neutral Engine Run-up (NERU) Test

To carry out this test, proceed as follows:

• Install a tachometer.
• Increase the engine rpm up from an idle to approximately 3,500 rpm while in PARK on front wheel drive vehicles with automatic transmissions, or NEUTRAL for all other vehicles. Note the engine rpm and, if possible, determine the vibration frequency.
• Attempt to identify what part of the vehicle the concern is coming from.
• Attempt to identify the source of the concern.
• Proceed as necessary.

Drive Engine Run-Up (DERU) Load Test

To carry out this test, proceed as follows:

•  WARNING: Block the front and rear wheels, and apply the parking brake and the service brake, or injury to personnel can result.

   CAUTION: Do not carry out the Engine Load Test for more than five seconds or damage to the transmission or transaxle can result.

  Block the front and rear wheels.
• Apply the parking brake and the service brake.
• Install a tachometer.
• Shift the transmission into DRIVE, and increase and decrease the engine rpm between an idle to approximately 2,000 rpm. Note the engine rpm and, if possible, determine the vibration frequency.
• Repeat the test in REVERSE.
• If the vibration or noise is duplicated when carrying out this test, inspect the engine and transmission or transaxle mounts.
• If the concern is definitely engine speed-related, carry out the Engine Accessory Test to narrow down the source.
• Proceed as necessary.

Engine Accessory Test

To carry out this test, proceed as follows:

•  WARNING: Block the front and rear wheels, and apply the parking brake and the service brake, or injury to personnel can result.

   CAUTION: Limit engine running time to one minute or less with belts removed or serious engine damage will result.

  NOTE: A serpentine drive belt decreases the usefulness of this test. In these cases, use a vibration analyzer, such as the EVA, to pinpoint accessory vibrations. An electronic listening device, such as an EngineEAR, will also help to identify noises from specific accessories.

  Remove the accessory drive belts.
• Increase the engine rpm to where the concern occurs.
• If the vibration/noise is duplicated when carrying out this test, the belts and accessories are not sources.
• If the vibration/noise was not duplicated when carrying out this test, install each accessory belt, one at a time, to locate the source.

Vehicle Cold Soak Procedure

To carry out this procedure, proceed as follows:

• Test preparations include matching customer conditions (if known). If not known, document the test conditions: gear selection and engine rpm. Monitor the vibration/noise duration with a watch for up to three minutes.
• Park the vehicle where testing will occur. The vehicle must remain at or below the concern temperature (if known) for 6-8 hours.
• Before starting the engine, conduct a visual inspection under the hood.
• Turn the key on, but do not start the engine. Listen for the fuel pump, anti-lock brake system (ABS) and air suspension system noises.
• Start the engine.

•  CAUTION: Never probe moving parts.

  Isolate the vibration/noise by carefully listening. Move around the vehicle while listening to find the general location of the vibration/noise. Then, search for a more precise location by using a stethoscope or EngineEAR.
• Refer to Idle Noise/Vibration in the Symptom Chart to assist with the diagnosis.

6: Check OASIS/TSBs/Repair History

After verifying the customer concern, check for OASIS reports, TSBs and the vehicle repair history for related concerns. If information relating to a diagnosis/repair is found, carry out the procedure(s) specified in that information.

If no information is available from these sources, carry out the vehicle preliminary inspection to eliminate any obvious faults.

7: Diagnostic Procedure

Qualifying the concern by the particular sensation present can help narrow down the concern. Always use the "symptom" to "system" to "component" to "cause" diagnosis technique. This diagnostic method divides the problem into related areas to correct the customer concern.

• Verify the "symptom".
• Determine which "system(s)" can cause the "symptom".
  • If a vibration concern is vehicle speed related, the tire and wheel rpm/frequency or driveshaft frequency should be calculated.
  • If a vibration concern is engine speed related, the engine, engine accessory or engine firing frequencies should be calculated.
• After determining the "system", use the diagnostic tools to identify the worn or damaged "components".
• After identifying the "components", try to find the "cause" of the failure.

Once the concern is narrowed down to a symptom/condition, proceed to NVH Condition and Symptom Categories.

NVH Condition and Symptom Categories

Operating Condition—Vehicle is Not Moving

1. Static operation
   • Noise occurs during part/system functioning. GO to Symptom Chart — Squeak and Rattle.

2. While cranking
   1. Grinding or whine, differential ring gear or starter motor pinion noise. GO to Symptom Chart — Engine Noise/Vibration.
   2. Rattle. Exhaust hanger, exhaust heat shield or A/C line noise. GO to Symptom Chart — Squeak and Rattle.
   3. Vibration. Acceptable condition.

3. At idle
   • Idle noise. GO to Symptom Chart — Idle Noise/Vibration.
   • Idle vibration or shake. GO to Symptom Chart — Idle Noise/Vibration.

4. During gear selection
   1. Vehicle parked on a steep incline. Acceptable noise.
   2. Vehicle parked on a flat surface. GO to Symptom Chart — Driveline Noise/Vibration.
   3. Vehicle with a manual transmission. GO to Symptom Chart — Transmission (Manual) and Transfer Case Noise/Vibration.

Operating Condition—Vehicle is Moving

1. Depends more on how the vehicle is operated
   1. Speed-related
      • Related to vehicle speed
        • Pitch increases with vehicle speed. GO to Symptom Chart — Tire Noise/Vibration.
        • Noise occurs at specific vehicle speed. A high-pitch noise (whine). GO to Symptom Chart — Drivline Noise/Vibration.
        • Loudness proportional to vehicle speed. Low-frequency noise at high speeds, noise and loudness increase with speed. GO to Symptom Chart — Driveline Noise/Vibration.
        • A low-pitched noise (drumming). GO to Symptom Chart — Engine Noise/Vibration.
        • Vibration occurs at a particular speed (mph) regardless of acceleration or deceleration. GO to Symptom Chart — Tire Noise/Vibration.
        • Noise varies with wind/vehicle speed and direction. GO to Symptom Chart — Air Leak and Wind Noise.
      • Related to engine speed.
        • Noise varies with engine rpm. GO to Symptom Chart — Engine Noise/Vibration.
        • Vibration occurs at a particular speed (mph) regardless of engine speed (rpm).
   2. Acceleration
      • Wide open throttle (WOT)
        • Engine induced contact between components. Inspect and repair as necessary.
        • Noise is continuous throughout WOT. Exhaust system or engine ground out. GO to Symptom Chart — Engine Noise/Vibration.
      • Light/moderate acceleration
        • Tip-in moan. Engine/exhaust noise. GO to Symptom Chart — Engine Noise/Vibration.
        • Knock-type noise. GO to Symptom Chart — Engine Noise/Vibration.
        • Driveline shudder. GO to Symptom Chart — Driveline Noise/Vibration.
        • Engine vibration. GO to Symptom Chart — Engine Noise/Vibration.
   3. Turning noise. GO to Symptom Chart —Steering Noise/Vibration.
   4. Braking.
      • Clicking sound is signaling ABS is active. Acceptable ABS sound.
      • A continuous grinding/squeal. GO to Symptom Chart — Brake Noise/Vibration.
      • Brake vibration/shudder. GO to Symptom Chart — Brake Noise/Vibration.
   5. Clutching.
      • A noise occurring during clutch operation. GO to Symptom Chart — Transmission (Manual) and Transfer Case Noise/Vibration.
      • Vibration. GO to Symptom Chart — Transmission (Manual) and Transfer Case Noise/Vibration.
   6. Shifting
      • Noise or vibration condition related to the transmission (automatic). GO to Symptom Chart — Transmission (Automatic) Noise/Vibration.
      • Noise or vibration related to the transmission (manual). GO to Symptom Chart — Transmission (Manual) and Transfer Case Noise/Vibration.
   7. Engaged in four-wheel drive. GO to Symptom Chart — Transmission (Manual) and Transfer Case Noise/Vibration.
   8. Cruising speeds
      • Accelerator pedal vibration. GO to Symptom Chart — Engine Noise/Vibration.
      • Driveline vibration. GO to Symptom Chart — Driveline Noise/Vibration.
      • A shimmy or shake. GO to Symptom Chart — Tire Noise/Vibration.
   9. Driving at low/medium speeds
      • A wobble or shudder. GO to Symptom Chart — Tire Noise/Vibration.

2. Depends more on where the vehicle is operated
   1. Bump/pothole, rough road or smooth road. GO to Symptom Chart — Suspension Noise/Vibration.
      • Noise is random or intermittent occurring from road irregularities. GO to Symptom Chart — Squeak and Rattle.
      • Noise or vibration changes from one road surface to another. Normal sound changes.
      • Noise or vibration associated with a hard/firm ride. GO to Symptom Chart — Suspension Noise/Vibration.

Symptom Charts

Pinpoint Tests

The pinpoint tests are a step-by-step diagnostic process designed to determine the cause of a condition. It may not always be necessary to follow a pinpoint test to its conclusion. Carry out only the steps necessary to correct the condition. Then, test the system for normal operation. Sometimes, it is necessary to remove various vehicle components to gain access to the component requiring testing. For additional information, refer to the appropriate section for removal and installation procedures. Reinstall all components after verifying system operation is normal.

PINPOINT TEST A: BRAKE VIBRATION/SHUDDER

CONDITIONS	DETAILS/RESULTS/ACTIONS
A1 ROAD TEST THE VEHICLE—LIGHT BRAKING
	Check that the wheel and tires are correct for the vehicle. Inspect the tires for abnormal wear patterns.
	Road test the vehicle. Warm the brakes by slowing the vehicle a few times from 80–32 km/h (50 to 20 mph) using light braking applications. At highway speeds of 89–97 km/h (55-60 mph), apply the brake using a light pedal force.
	Is there a vibration/shudder felt in the steering wheel, seat or brake pedal? Yes GO to A4. No GO to A2.
A2 ROAD TEST THE VEHICLE—MODERATE TO HEAVY BRAKING
	Road test the vehicle. At highway speeds of 89–97 km/h (55-60 mph), apply the brake using a moderate to heavy pedal force.
	Is there a vibration/shudder? Yes For vehicles with ABS, GO to A3. For vehicles with standard brakes, GO to A4. No Vehicle is OK. VERIFY condition with customer. TEST the vehicle for normal operation.
A3 NORMAL ACTUATION OF THE ABS SYSTEM DIAGNOSIS
	During moderate to heavy braking, noise from the hydraulic control unit (HCU) and pulsation in the brake pedal can be observed. Pedal pulsation coupled with noise during heavy braking or on loose gravel, bumps, wet or snowy surfaces is acceptable and indicates correct functioning of the ABS system. Pedal pulsation or steering wheel nibble whose frequency is proportioned to the vehicle speed indicates a concern with a brake or suspension component.
	Is the vibration/shudder vehicle speed sensitive? Yes GO to A5. No The brake system is operating correctly.
A4 APPLICATION OF THE PARKING BRAKE
	NOTE: Begin at the front of the vehicle unless the vibration or shudder has been isolated to the rear. This test is not applicable to vehicles with drum-in-hat type parking brakes. For vehicles with drum-in-hat parking brakes, proceed to the next test. For all other vehicles, apply the parking brake to identify if the problem is in the front or rear brake. At highway speeds of 89–97 km/h (55-60 mph), lightly apply the parking brake until the vehicle slows down. Release the parking brake immediately after the test.
	Is there a vibration/shudder? Yes GO to A8. No GO to A5.
A5 CHECK THE FRONT WHEEL BEARINGS
	Check the front wheel bearings. Refer to Wheel Bearing Check in this section.
	Are the wheel bearings OK? Yes GO to A6. No INSPECT the wheel bearings. ADJUST or REPAIR as necessary. TEST the system for normal operation.
A6 CHECK THE FRONT SUSPENSION
	Check the front suspension for: broken or loose bolts damaged springs worn or damaged lower control arm bushings loose or rough front bearings uneven tire wear
	Are all the suspension components in satisfactory condition? Yes GO to A7. No REPAIR or INSTALL new components as necessary. TEST the system for normal operation.
A7 RESURFACE THE FRONT BRAKE DISCS
	CAUTION: Do not use a bench lathe to machine brake discs. NOTE: Follow the manufacturer's instructions to machine the brake discs. After machining, make sure the brake disc meets the thickness specification. Refer to Brake Disc Machining in this section. Resurface the front brake discs. Road test the vehicle.
	Is the vibration/shudder present? Yes GO to A8. No Vehicle is OK.
A8 CHECK THE REAR SUSPENSION
	Check the rear suspension for: broken or loose bolts damaged or worn springs or spring bushings worn or damaged upper and lower control arm bushings worn or damaged trailing arms loose or rough rear bearings uneven tire wear
	Are all the suspension components in satisfactory condition? Yes GO to A9. No REPAIR or INSTALL new components as necessary. TEST the system for normal operation.
A9 RESURFACE THE REAR BRAKE DISC OR DRUM
	CAUTION: Do not use a bench lathe to machine brake discs. NOTE: Follow the manufacturers instructions to machine the brake discs. After machining, make sure the brake disc meets the thickness specification. Refer to Brake Disc Machining in this section. Resurface the rear brake disc or drums. Road test the vehicle.
	Is the vibration/shudder present? Yes CHECK the front suspension for wear or damage, RESURFACE the front brake discs. TEST the system for normal operation. No Vehicle is OK.

PINPOINT TEST B: ENGINE TICKING NOISE

CONDITIONS	DETAILS/RESULTS/ACTIONS
B1 CHECK FOR TICKING NOISE AT THE FUEL RAIL
	Disconnect the first fuel line clip.
	Is the ticking noise gone? Yes CHECK for TSB for applicable vehicle. REPAIR as necessary. TEST the system for normal operation. No GO to B2.
B2 CHECK FOR TICKING NOISE AT THE FUEL INJECTOR
	Using an EngineEAR, listen at the fuel injectors by placing a probe on each injector. To isolate the faulty injector, disconnect the injector electrical connector and listen for the noise.
	Is the fuel injector the source of the ticking noise? Yes INSTALL a new fuel injector. REFER to Section 303-04A for 2.0L Zetec engine or Section 303-04B for 3.0L (4V) engine. TEST the system for normal operation. No GO to B3.
B3 CHECK THE BELT TENSIONER FOR TICKING NOISE
	Inspect the front engine accessory drive (FEAD). Check for the belt tensioner bottoming at end of travel or not at end of stroke.
	Using an EngineEAR, listen at the belt tensioner.
	Is the belt tensioner the source of the noise? Yes INSTALL a new belt tensioner. REFER to Section 303-05. TEST the system for normal operation. No GO to B4.
B4 CHECK THE WATER PUMP FOR TICKING NOISE
	Using an EngineEAR, listen at the water pump for ticking noise.
	Is the water pump the source of the noise? Yes INSTALL a new water pump. REFER to Section 303-03. TEST the system for normal operation. No GO to B5.
B5 CHECK FOR AN OBSTRUCTION OF THE COOLING FAN
	Inspect the cooling fan for obstructions.
	Check the cooling fan and shroud for wear or damage.
	Was there an obstruction or does the cooling fan show signs of damage? Yes REPAIR or INSTALL a new cooling fan. REFER to Section 303-03. TEST the system for normal operation. No GO to B6.
B6 CHECK THE OIL PUMP FOR TICKING NOISE
	Check the oil pump using EngineEARs and probe at the oil filter adapter to verify the oil pump as a source.
	Is the oil pump the source of the noise? Yes INSTALL a new oil pump. REFER to Section 303-01A for 2.0L Zetec engine or Section 303-01B for 3.0L (4V) engine. TEST the system for normal operation. No GO to B7.
B7 CHECK VALVE LIFTERS OR LASH ADJUSTERS FOR CORRECT OPERATION
	Check valve lifter/lash adjuster for correct operation, using EngineEARs.
	Are the valve lifters/lash adjusters operating correctly? Yes VERIFY customer concern. CONDUCT a diagnosis of other suspect components. No INSTALL a new valve lifter/lash adjuster(s). TEST the system for normal operation.

PINPOINT TEST C: FRONT ENGINE ACCESSORY DRIVE BEARING HOOT

CONDITIONS	DETAILS/RESULTS/ACTIONS
C1 CHECK THE ACCESSORY DRIVE IDLER AND TENSIONER PULLEY BEARINGS
	Carry out the Vehicle Cold Soak Procedure in this section.
	Place an EngineEAR probe directly on the pulley center post or bolt to verify which bearing is making the noise.
	Is either bearing making the noise? Yes INSTALL a new pulley/idler. REFER to Section 303-05. CARRY OUT the Vehicle Cold Soak Procedure and TEST the system for normal operation. No CONDUCT a diagnosis on other suspect accessory drive components.

PINPOINT TEST D: POWER STEERING MOAN

CONDITIONS	DETAILS/RESULTS/ACTIONS
D1 CHECK THE POWER STEERING SYSTEM
	Carry out the Vehicle Cold Soak Procedure in this section.
	Turn the steering wheel while the noise is occurring and listen for changes in sound pitch or loudness.
	Does the sound pitch or loudness change while turning the steering wheel? Yes GO to D2. No CONDUCT a diagnosis on other suspect accessory drive components.
D2 VERIFY THE SOURCE
	Place an EngineEAR probe near the power steering pump/reservoir while the noise is occurring. While an assistant turns the steering wheel, listen for changes in sound pitch or loudness.
	Does the sound pitch or loudness change while turning the steering wheel? Yes VERIFY that the supply tube to the pump is unobstructed. CHECK the fluid condition and level. DRAIN the fluid and REFILL. CARRY OUT the Vehicle Cold Soak Procedure and TEST the system for normal operation. REFER to Section 211-02. No Normal system operation.

PINPOINT TEST E: DRUMMING NOISE

CONDITIONS	DETAILS/RESULTS/ACTIONS
E1 CHECK THE EXHAUST SYSTEM
	Increase the engine rpm until the noise is the loudest. Note the engine rpm.
	Add approximately 9 kg (20 lb) of weight to the exhaust system. Place the weight at the tailpipe and test.
	Increase the engine rpm and listen for the drumming noise. Note the engine rpm if the noise occurs.
	Using a vibration analyzer, determine the amount of vibration that occurs with the drumming noise.
	Is the noise/vibration reduced or eliminated, or does the noise/vibration occur at a different rpm? Yes CARRY OUT Exhaust System Neutralizing in this section. TEST the system for normal operation. No GO to E2.
E2 POWERTRAIN/DRIVETRAIN MOUNT NEUTRALIZING
	Carry out Powertrain/Drivetrain Mount Neutralizing in this section. Test the system for normal operation.
	Is the noise reduced or eliminated? Yes Vehicle is OK. TEST the system for normal operation. No CONDUCT diagnosis of other suspect components.

PINPOINT TEST F: ENGINE TICKING, KNOCKING OR CONTINUOUS RATTLE

CONDITIONS	DETAILS/RESULTS/ACTIONS
F1 CHECK FOR NOISE AT THE VALVE COVERS AND THE FRONT COVERS (OHC ENGINES)
	Carry out the Vehicle Cold Soak Procedure in this section.
	NOTE: For a short-duration ticking noise, multiple engine starts may be necessary. Using an EngineEAR, listen closely at the valve covers and the front covers by placing the probe near the surface of the valve cover and then on the surface front cover.
	Is the noise source apparent? Yes REMOVE the appropriate cover and INSPECT for loose, worn/broken components. REPAIR as necessary. TEST the system for normal operation. No GO to F2.
F2 CHECK FOR NOISE AT THE CYLINDER BLOCK
	Using an EngineEAR, listen closely at the cylinder block by placing a probe on or near each freeze plug.
	Is the noise source apparent? Yes REPAIR or INSTALL new components as necessary. No GO to F3.
F3 CHECK FOR NOISE WHILE DISCONNECTING EACH FUEL INJECTOR ELECTRICAL CONNECTOR, ONE AT A TIME
	Disconnect each fuel injector electrical connector, one at a time, to decrease piston force and listen for the noise.
	Is the noise reduced or eliminated? Yes INSTALL a new fuel injector. REFER to Section 303-04A for 2.0L Zetec engine or Section 303-04B for 3.0L (4V) engine. TEST the system for normal operation. No INSPECT accessory drive or the transmission as a possible source.

PINPOINT TEST G: FRONT SUSPENSION NOISE

CONDITIONS	DETAILS/RESULTS/ACTIONS
G1 ROAD TEST THE VEHICLE
	Test drive the vehicle.
	During the road test, drive the vehicle over a rough road. Using ChassisEARs, determine from which area/component the noise is originating.
	Is there a squeak, creak or rattle noise? Yes GO to G2. No The suspension system is OK. CONDUCT a diagnosis on other suspect systems.
G2 INSPECT THE STEERING SYSTEM
	Raise and support the vehicle. For additional information, refer to Section 100-02.
	Check the steering system for wear or damage. Carry out a steering linkage test.
	Inspect the tire wear pattern. Refer to Tire Wear Patterns chart in this section.
	Are the steering components worn or damaged? Yes REPAIR the steering system. INSTALL new components as necessary. TEST the system for normal operation. No GO to G3.
G3 FRONT SHOCK ABSORBER/STRUT CHECK
	Check the front shock absorbers/strut mounts for loose bolts or nuts.
	Check the front shock absorbers/struts for damage. Carry out a shock absorber check.
	Are the front shock absorbers/struts loose or damaged? Yes TIGHTEN to specifications if loose. INSTALL new front shock absorbers/struts if damaged. TEST the system for normal operation. No GO to G4.
G4 CHECK THE FRONT SPRINGS
	Check the front spring and front spring mounts/brackets for wear or damage.
	Are the front springs or spring mounts/brackets worn or damaged? Yes REPAIR or INSTALL new components as necessary. TEST the system for normal operation. No GO to G5.
G5 CHECK THE CONTROL ARMS/RADIUS ARMS
	Inspect the control arm bushings for wear or damage.
	Inspect for twisted or bent control arm/radius arm.
	Are the control arm/radius arms damaged or worn? Yes REPAIR or INSTALL new components as necessary. TEST the system for normal operation. No GO to G6.
G6 CHECK THE STABILIZER BAR/TRACK BAR
	Check the stabilizer bar/track bar bushings and links for damage or wear.
	Check the stabilizer bar/track bar for damage.
	Check for loose or damaged stabilizer bar/track bar isolators or brackets.
	Are the stabilizer bar/track bar components loose, worn or damaged? Yes REPAIR or INSTALL new components as necessary. TEST the system for normal operation. No Suspension system is OK. CONDUCT diagnosis on other suspect systems.

PINPOINT TEST H: REAR SUSPENSION NOISE

CONDITIONS	DETAILS/RESULTS/ACTIONS
H1 ROAD TEST THE VEHICLE
	Test drive the vehicle.
	During the road test, drive the vehicle over a rough road. Using ChassisEARs, determine from which area/component the noise is originating.
	Is there a squeak, creak or rattle noise? Yes GO to H2. No The suspension system is OK. Conduct a diagnosis on other suspect systems.
H2 REAR SHOCK ABSORBER/STRUT CHECK
	Raise and support the vehicle. REFER to Section 100-02.
	Check the rear shock absorber/strut mounts for loose bolts or nuts.
	Check the rear shock absorbers/struts for damage. Carry out a shock absorber check.
	Are the rear shock absorbers/struts loose or damaged? Yes TIGHTEN to specifications if loose. INSTALL new rear shock absorbers/struts if damaged. TEST the system for normal operation. No GO to H3.
H3 CHECK THE REAR SPRINGS
	Check the rear springs and rear spring mounts/brackets for wear or damage.
	Are the rear springs or spring mounts/brackets worn or damaged? Yes REPAIR or INSTALL new components as necessary. TEST the system for normal operation. No GO to H4.
H4 CHECK THE CONTROL ARMS/TRAILING ARMS
	Inspect the control arm/trailing arm bushings for wear or damage. Check for loose control arm/trailing arm bolts.
	Inspect for twisted or bent control arms/trailing arms.
	Are the control arms/trailing arms loose, damaged or worn? Yes REPAIR or INSTALL new components as necessary. TEST the system for normal operation. No Suspension system is OK. CONDUCT diagnosis on other suspect systems.

PINPOINT TEST I: WHEEL AND TIRE

CONDITIONS	DETAILS/RESULTS/ACTIONS
I1 ROAD TEST THE VEHICLE
	NOTE: Wheel or tire vibrations felt in the steering wheel are most likely related to the front wheel or tire. Vibration felt through the seat are most likely related to the rear wheel or tire. This may not always be true, but it can help to isolate the problem to the front or rear of the vehicle. Test drive the vehicle at different speed ranges.
	During the road test, if the vibration can be eliminated by placing the vehicle in neutral or is affected by the speed of the engine, the cause is not the wheels or tires.
	Is there a vibration and noise? Yes GO to I2. No The wheel and tires are OK. CONDUCT a diagnosis on other suspect systems.
I2 CHECK THE FRONT WHEEL BEARINGS
	Check the front wheel bearings. Refer to Wheel Bearing Check in this section.
	Are the wheel bearings OK? Yes GO to I3. No INSPECT the wheel bearings. ADJUST or REPAIR as necessary. TEST the system for normal operation.
I3 INSPECT THE TIRES
	Check the tires for missing weights.
	Check the wheels for damage.
	Inspect the tire wear pattern. Refer to the Tire Wear Patterns chart in this section.
	Do the tires have an abnormal wear pattern? Yes CORRECT the condition that caused the abnormal wear. INSTALL new tire(s). TEST the system for normal operation. No GO to I4.
I4 TIRE ROTATION DIAGNOSIS
	Spin the tires slowly and watch for signs of lateral runout.
	Spin the tires slowly and watch for signs of radial runout.
	Are there signs of visual runout? Yes GO to I5. No CHECK the wheel and tire balance. CORRECT as necessary. TEST the system for normal operation.
I5 RADIAL RUNOUT CHECK ON THE TIRE
	Measure the radial runout of the wheel and tire assembly. A typical specification for total radial runout is 1.15mm (0.059inch).
	Is the radial runout within specifications? Yes GO to I8. No GO to I6.
I6 RADIAL RUNOUT CHECK ON THE WHEEL
	Measure the radial runout of the wheel. A typical specification for total radial runout is 1.14mm (0.045 inch).
	Is the radial runout within specifications? Yes INSTALL a new tire. TEST the system for normal operation. No GO to I7.
I7 CHECK THE HUB/BRAKE DISC OR DRUM PILOT RUNOUT OR BOLT CIRCLE RUNOUT
	Measure the pilot or bolt circle runout. A typical specification for radial runout is: pilot runout— less than 0.15 mm (0.006 inch) bolt circle runout— less than 0.38 mm (0.015 inch)
	Is the radial runout within specifications? Yes INSTALL a new wheel. TEST the system for normal operation. No REPAIR or INSTALL new components as necessary. REFER to Section 204-01 for the front suspension or Section 204-02 for the rear suspension.
I8 LATERAL RUNOUT CHECK ON THE TIRE
	Measure the lateral runout of the wheel and tire assembly. A typical specification for total lateral runout is 2.5mm (0.098inch).
	Is the lateral runout within specifications? Yes Wheel and tires are OK. CONDUCT diagnosis on other suspect systems. No GO to I9.
I9 LATERAL RUNOUT CHECK ON THE WHEEL
	Measure the lateral runout of the wheel. A typical specification for total radial runout is 1.2mm (0.047inch).
	Is the lateral runout within specifications? Yes INSTALL a new tire. TEST the system for normal operation. No GO to I10.
I10 CHECK THE FLANGE FACE LATERAL RUNOUT
	Measure the flange face lateral runout. A typical specification for lateral runout is: hub/brake disc— less than 0.13mm (0.005inch) axle shaft— less than 0.25 mm (0.010 inch)
	Is the lateral runout within specifications? Yes INSTALL a new wheel. TEST the system for normal operation. No REPAIR or INSTALL new components as necessary. REFER to Section 204-01 for the front suspension or Section 204-02 for the rear suspension.

PINPOINT TEST J: HIGH SPEED SHAKE OR SHIMMY

CONDITIONS	DETAILS/RESULTS/ACTIONS
J1 CHECK FOR FRONT WHEEL BEARING ROUGHNESS
	Chock the rear wheels.
	Raise and support the front end of the vehicle so that the front wheel and tire assemblies can spin. Refer to Section 100-02.
	Spin the front tires by hand.
	Do the wheel bearings feel rough? Yes INSPECT the wheel bearings. REPAIR as necessary. TEST the system for normal operation. No GO to J2.
J2 CHECK THE END PLAY OF THE FRONT WHEEL BEARINGS
	Check the end play of the front wheel bearings.
	Is the end play OK? Yes GO to J3. No ADJUST or REPAIR as necessary. TEST the system for normal operation.
J3 MEASURE THE LATERAL RUNOUT AND THE RADIAL RUNOUT OF THE FRONT WHEELS ON THE VEHICLE
	Measure the lateral runout and the radial runout of the front wheels on the vehicle. Go to Pinpoint Test I.
	Are the measurements within specifications? Yes GO to J4. No INSTALL new wheels as necessary and BALANCE the assembly. TEST the system for normal operation.
J4 MEASURE THE LATERAL RUNOUT OF THE FRONT TIRES ON THE VEHICLE
	Measure the lateral runout of the front tires on the vehicle. Go to Pinpoint Test I.
	Is the runout within specifications? Yes GO to J5. No INSTALL new tires as necessary and BALANCE the assembly. TEST the system for normal operation.
J5 MEASURE THE RADIAL RUNOUT OF THE FRONT TIRES ON THE VEHICLE
	Measure the radial runout of the front tires on the vehicle. Go to Pinpoint Test I.
	Is the runout within specifications? Yes BALANCE the front wheel and tire assemblies. If any tire cannot be balanced, INSTALL a new tire. TEST the system for normal operation. No GO to J6.
J6 MATCH MOUNT THE TIRE AND WHEEL ASSEMBLY
	Mark the high runout location on the tire and also on the wheel. Break the assembly down and rotate the tire 180 degrees (halfway around) on the wheel. Inflate the tire and measure the radial runout.
	Is the runout within specifications? Yes BALANCE the assembly. TEST the system for normal operation. No If the high spot is not within 101.6 mm (4 inches) of the first high spot on the tire, GO to J7.
J7 MEASURE THE WHEEL FLANGE RUNOUT
	Dismount the tire and mount the wheel on a wheel balancer. Measure the runout on both wheel flanges. Go to Pinpoint Test I.
	Is the runout within specifications? Yes LOCATE and MARK the low spot on the wheel. INSTALL the tire, matching the high spot on the tire with the low spot on the wheel. BALANCE the assembly. TEST the system for normal operation. If the condition persists,GO to J8. No INSTALL a new wheel. CHECK the runout on the new wheel. If the new wheel is within limits, LOCATE and MARK the low spot. INSTALL the tire, matching the high spot on the tire with the low spot on the wheel. BALANCE the assembly. TEST the system for normal operation. If the condition persists, GO to J8.
J8 CHECK FOR VIBRATION FROM THE FRONT OF THE VEHICLE
WARNING: If only one drive wheel is allowed to rotate, speed must be limited to 55 km/h (34 mph) using the speedometer reading, since actual wheel speed will be twice that indicated on the speedometer. Exceeding a speed of 55 km/h (34 mph) or allowing the drive wheel to hang unsupported can result in tire disintegration or differential failure, which can cause serious personal injury and extensive vehicle damage.
	Spin the front wheel and tire assemblies with a wheel balancer while the vehicle is raised on a hoist. Feel for vibration in the front fender or while seated in the vehicle.
	Is the vibration present? Yes SUBSTITUTE known good wheel and tire assemblies as necessary. TEST the system for normal operation. No For front wheel drive vehicles, check the driveline components. TEST the system for normal operation. For rear wheel drive vehicles, GO to J9.
J9 CHECK FOR VIBRATION FROM THE REAR OF THE VEHICLE
WARNING: If only one drive wheel is allowed to rotate, speed must be limited to 55 km/h (34 mph) using the speedometer reading, since actual wheel speed will be twice that indicated on the speedometer. Exceeding a speed of 55 km/h (34 mph) or allowing the drive wheel to hang unsupported can result in tire disintegration or differential failure, which can cause serious personal injury and extensive vehicle damage.
	Chock the front wheels.
	Raise and support the rear end of the vehicle so that the rear wheel and tire assemblies can spin. Refer to Section 100-02.
	Engage the drivetrain and carefully accelerate the drive wheels while checking for vibration.
	Is the vibration present? Yes GO to J10. No TEST the system for normal operation.
J10 CHECK THE DRIVETRAIN
WARNING: If only one drive wheel is allowed to rotate, speed must be limited to 55 km/h (34 mph) using the speedometer reading, since actual wheel speed will be twice that indicated on the speedometer. Exceeding a speed of 55 km/h (34 mph) or allowing the drive wheel to hang unsupported can result in tire disintegration or differential failure, which can cause serious personal injury and extensive vehicle damage.
	Remove the rear wheel and tire assemblies. Refer to Section 204-04.
	Secure the brake drums (if so equipped), by installing wheel hub bolt nuts, reversed.
	Carefully accelerate the drivetrain while checking for vibration.
	Is the vibration present? Yes CHECK/TEST the drivetrain and driveline components. TEST the system for normal operation. No SUBSTITUTE known good wheel and tire assemblies as necessary. TEST the system for normal operation.

PINPOINT TEST K: CLUTCH VIBRATION

CONDITIONS	DETAILS/RESULTS/ACTIONS
K1 CHECK ENGINE COMPONENTS FOR GROUNDING
	NOTE: Make sure the clutch is the cause of the vibration concern. The vibration should occur during clutch operation. The clutch can also be difficult to engage or disengage. Eliminate all related systems before checking the clutch components. NOTE: Check the driveline angles and driveshaft runout before disassembling the clutch system. Refer to Section 205-00 for the correct driveline angle specifications. Check the powertrain/drivetrain mounts, exhaust manifolds or other engine components for grounding on the chassis.
	Are any mounts or engine components grounded? Yes REPAIR as necessary. TEST the system for normal operation. No GO to K2.
K2 CHECK THE ACCESSORY DRIVE BELT
	Remove the accessory drive belt.
	Does the vibration stop with the accessory drive belt removed? Yes DIAGNOSE the accessory drive components. No GO to K3.
K3 CHECK FOR LOOSE CLUTCH PRESSURE PLATE BOLTS
	Check for loose clutch pressure plate bolts. Inspect the clutch pressure plate for damage or for material between the pressure plate and flywheel.
	Are there any loose bolts or damage? Yes TIGHTEN the bolts to specifications or if damaged, INSTALL a new clutch pressure plate. REFER to Section 308-01. TEST the system for normal operation. No GO to K4.
K4 CHECK THE CLUTCH DISC SPRINGS
	Check for worn, broken or loose clutch disc springs.
	Are the clutch springs worn, broken or loose? Yes INSTALL a new clutch disc. REFER to Section 308-01. TEST the system for normal operation. No GO to K5.
K5 CHECK THE CLUTCH DISC SPLINES
	Inspect the clutch disc splines for damage or wear.
	Is there damage or wear? Yes INSTALL a new clutch disc. REFER to Section 308-01. TEST the system for normal operation. No GO to K6.
K6 CHECK THE FLYWHEEL BOLTS
	Check for loose flywheel bolts.
	Are the bolts loose? Yes TIGHTEN the bolts to specifications. REFER to Section 308-01. TEST the system for normal operation. No GO to K7.
K7 CHECK THE FLYWHEEL SURFACE
	Inspect the flywheel surface for wear or damage. Check the flywheel runout.
	Is there any damage or excessive wear? Yes INSTALL a new flywheel. REFER to Section 303-01A for 2.0L Zetec engine or Section 303-01B for 3.0L (4V) engine. TEST the system for normal operation. No Clutch system is normal. CONDUCT a diagnosis on other suspect systems.

PINPOINT TEST L: TRANSFER CASE VIBRATION

CONDITIONS	DETAILS/RESULTS/ACTIONS
L1 INSPECT THE TRANSFER CASE
	Inspect the transfer case for loose or missing mounting bolts. Check for fluid seepage between the transfer case and the transmission.
	Are the mounting bolts missing or loose? Yes TIGHTEN to specifications or INSTALL new bolts as necessary. REFER to Section 308-07B. TEST the system for normal operation. No GO to L2.
L2 INSPECT THE REAR DRIVESHAFT
	NOTE: Verify that the driveshaft and pinion flange index marks are aligned. Inspect the driveshaft for missing weights, damage or undercoating.
	Inspect the U-joints for freedom of movement.
	Inspect the constant velocity joint for freedom of movement.
	Check driveshaft runout and, if necessary, check the pinion flange runout.
	Are the driveshaft or U-joints worn or damaged or misaligned? Yes INSTALL a new driveshaft as necessary. TEST the system for normal operation. No GO to L3.
L3 CHECK THE DRIVELINE ANGLES
	Measure the rear driveshaft and pinion angles. Refer to Section 205-00.
	Measure the front driveshaft and pinion angles. Refer to Section 205-00.
	Are the driveline angles incorrect? Yes REPAIR as necessary. TEST the system for normal operation. No GO to L4.
L4 ROAD TEST WITH THE REAR DRIVESHAFT REMOVED
	NOTE: Index mark the driveshaft to the pinion flange and to the output shaft before removal. Remove the rear driveshaft.
	Test drive the vehicle.
	Is the vibration gone? Yes INSTALL and BALANCE the rear driveshaft. TEST the system for normal operation. No GO to L5.
L5 TRANSFER CASE OUTPUT FLANGE INSPECTION
	Inspect the output flange for damage.
	Inspect the driveshaft constant velocity joints for wear or damage.
	Are the splines worn or damaged? Yes REPAIR or INSTALL new components as necessary. TEST the system for normal operation. No The transfer case is OK. CONDUCT a diagnosis on other suspect systems.

Component Tests

Idle Air Control (IAC) Valve

1. Open the hood.

2. NOTE: Key symptom is elevated idle speed while noise is occurring.

   NOTE: "Snapping" the throttle can induce the noise.

   Verify the condition by operating the vehicle for a short time.

3. Inspect the IAC. If physical evidence of contamination exists, install a new IAC.

4. While the noise is occurring, either place an EngineEAR probe near the IAC valve and the inlet tube, or create a 6.35 mm (0.25 in)-12.7 mm (0.50 in) air gap between the inlet tube and the clean air tube. If the IAC valve is making the noise, install a new IAC valve.

5. Test the vehicle for normal operation.

Steering Gear Grunt/Shudder Test

1. Start and run the vehicle to operating temperature.

2. Set engine idle speed to 1,200 rpm.

3.  CAUTION: Do not hold the steering wheel against the stops for more than three to five seconds at a time. Damage to the power steering pump will occur.

   Rotate the steering wheel to the RH stop, then turn the steering wheel 90 degrees back from that position. Turn the steering wheel slowly in a 15 to 30 degree arc.

4. Turn the steering wheel another 90 degrees. Turn the steering wheel slowly in a 15 to 30 degree arc.

5. Repeat the test with power steering fluid at different temperatures.

6. If a light grunt is heard or a low (50-200 Hz) shudder is present, this is a normal steering system condition.

7. If a loud grunt is heard or a strong shudder is felt, fill and purge the power steering system.

Checking Tooth Contact Pattern and Condition of the Ring and Pinion

There are two basic types of conditions that will produce ring and pinion noise. The first type is a howl or chuckle produced by broken, cracked, chipped, scored or forcibly damaged gear teeth and is usually quite audible over the entire speed range. The second type of ring and pinion noise pertains to the mesh pattern of the gear pattern. This gear noise can be recognized as it produces a cycling pitch or whine. Ring and pinion noise tends to peak in a narrow speed range or ranges, and will tend to remain constant in pitch.

1. Raise and support the vehicle. Refer to Section 100-02.

2. Drain the axle lubricant. Refer to Section 205-02.

3. Remove the carrier assembly or the axle housing cover depending on the axle type. Refer to Section 205-02.

4. Inspect the gear set for scoring or damage.

5. In the following steps, the movement of the contact pattern along the length is indicated as toward the" heel" or "toe" of the differential ring gear.

6. Apply a marking compound to a third of the gear teeth on the differential ring gear. Rotate the differential ring gear several complete turns in both directions until a good, clear tooth pattern is obtained. Inspect the contact patterns on the ring gear teeth.

7. A good contact pattern should be centered on the tooth. It can also be slightly toward the toe. There should always be some clearance between the contact pattern and the top of the tooth.

• Tooth contact pattern shown on the drive side of the gear teeth.

8. A high, thick contact pattern that is worn more toward the toe.

• Tooth contact pattern shown on the drive side of the gear teeth.
• The high contact pattern indicates that the drive pinion is not installed deep enough into the carrier.
• The differential ring gear backlash is correct, a thinner drive pinion shim is needed. A decrease will move the drive pinion toward the differential ring gear.

9. A high, thin contact pattern that is worn toward the toe.

• Tooth contact pattern shown on the drive side of the gear teeth.
• The drive pinion depth is correct. Increase the differential ring gear backlash.

10. A contact pattern that is worn in the center of the differential ring gear tooth toward the heel.

• Tooth contact pattern shown on the drive side of the gear teeth.
• The low contact pattern indicates that the drive pinion is installed too deep into the carrier.
• The differential ring gear backlash is correct. A thicker drive pinion shim is needed.

11. A contact pattern that is worn at the top of the differential ring gear tooth toward the heel.

• Tooth contact pattern shown on the drive side of the gear teeth.
• The pinion gear depth is correct. Decrease the differential ring gear backlash.

Tire Wear Patterns and Frequency Calculations

Tire Wear Chart

Wheel and tire NVH concerns are directly related to vehicle speed and are not generally affected by acceleration, coasting or decelerating. Also, out-of-balance wheel and tires can vibrate at more than one speed. A vibration that is affected by the engine rpm, or is eliminated by placing the transmission in NEUTRAL is not related to the tire and wheel. As a general rule, tire and wheel vibrations felt in the steering wheel are related to the front tire and wheel assemblies. Vibrations felt in the seat or floor are related to the rear tire and wheel assemblies. This can initially isolate a concern to the front or rear.

Careful attention must be paid to the tire and wheels. There are several symptoms that can be caused by damaged or worn tire and wheels. Carry out a careful visual inspection of the tires and wheel assemblies. Spin the tires slowly and watch for signs of lateral or radial runout. Refer to the tire wear chart to determine the tire wear conditions and actions.

For a vibration concern, use the vehicle speed to determine tire/wheel frequency and rpm. Calculate tire and wheel rpm and frequency by carrying out and following:

• Measure the diameter of the tire.
• Record the speed at which the vibration occurs.
• Obtain the corresponding tire and wheel rpm and frequency from the Tire Speed and Frequency Chart.
  • If the vehicle speed is not listed, divide the vehicle speed at which the vibration occurs by 16 (km/h (10 mph). Multiply that number by 16 km/h (10 mph) tire rpm listed for that tire diameter in the chart. Then divide that number by 60. For example: a 40 mph vibration with 835 mm (33 in) tires. 40 ÷10 = 4. Multiply 4 by 105 = 420 rpm. Divide 420 rpm by 60 seconds = 7 Hz at 40mph.