Pinpoint Tests

These pinpoint tests are designed to take the technician through a step-by-step diagnosis procedure to determine the cause of a condition. It may not always be necessary to follow a chart to its conclusion. Perform only the steps necessary to correct the condition. Then check the operation of the system to be sure the condition has been corrected.

It is sometimes necessary to remove various vehicle components to gain access to the component to be tested. Refer to the applicable section for removal and installation of components. After verifying that the condition has been corrected, make sure all components removed have been reinstalled.

When performing Pinpoint Test A, Shake/Vibration in Drive Under Acceleration/Deceleration diagnosis or Pinpoint TestD, Engine Accessory Vibration diagnosis, observe the following precautions:

 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 COULD RESULT IN TIRE DISINTEGRATION AND/OR DIFFERENTIAL FAILURE, WHICH COULD CAUSE SERIOUS PERSONAL INJURY AND EXTENSIVE VEHICLE DAMAGE.

PINPOINT TEST A: SHAKE/VIBRATION IN DRIVE UNDER ACCESSORY/DECELERATION

A1 ROAD TEST FOR SHAKE/VIBRATION

• Accelerate vehicle to the speed at which the customer indicated the shake/vibration occurred.
• Record the critical vehicle speed and/or engine rpm.
• Place transmission in neutral and allow engine to return to idle.

A2 INSPECT TIRES/WHEELS

• Raise vehicle on a frame contact hoist. Inspect tires/wheels for extreme wear or damage, cupping or flat spots.

A3 INSPECT WHEEL BEARINGS

• Spin tires by hand to check for wheel bearing roughness. Check wheel bearing end play. Refer to Section 04-01A or Section 04-01B.

A4 TIRE/WHEEL BALANCE

• Check tire/wheel balance. Refer to Section 04-04. Correct as needed.
• Road test.

A5 MEASURE RUNOUTS

• For each wheel position measure, locate and mark the following:
• High point of tire/wheel assembly total radial runout.
• High point of wheel radial runout.
• High point of wheel lateral runout.





• Record all measurements in chart below




Assembly Position	Tire/Wheel Assembly Total Radial Runout	Wheel Radial Runout	Wheel Lateral Runout
Left Front
Right Front
Left Rear
Right Rear
Example	1.52mm (0.060 Inch)	0.50mm (0.020 Inch)	0.63mm (0.025 Inch)

A6 ANALYSIS OF RUNOUT MEASUREMENT

• Measurements obtained in A5 must fall within guidelines below.

A7 WHEEL HUB BOLT RUNOUT

• Wheel hub bolt runout can affect wheel runout. Remove wheels and inspect wheel hub bolts.
• Measure wheel hub bolt runout. Refer to Section 04-04.





• Wheel hub bolt circle runout should not exceed 0.41mm (0.016 inch) TIR (total indicated runout).

A8 WHEEL PILOT RADIAL RUNOUT

• Zero the indicator and slowly rotate axle shaft one complete revolution.
• Record total deflection.
• Wheel pilot radial runout should not exceed 0.254 mm (0.010 inch) TIR (total indicated runout).

A9 FLANGE FACE LATERAL RUNOUT

• Zero the indicator and slowly rotate the axle shaft one complete revolution.
• Record total deflection.
• Flange face lateral runout should not exceed 0.152mm (0.006 inch) for disc brakes or 0.508mm (0.020 inch) for drum brakes TIR (total indicated runout).

A10 REPLACING A WHEEL

• Measure the runouts on the new assembly.

A11 INDEX TIRE/WHEEL ASSEMBLY

• Align high point of total assembly radial runout 180 degrees away from high point of wheel radial runout.
• Measure total assembly radial runout.

A12 REPLACE A TIRE

• Measure total assembly radial runout on new assembly.

A13 ROAD TEST

• Balance new tire/wheel assembly.
• After all assemblies have been checked and corrected, road test vehicle.

A14 SUBSTITUTE WHEELS AND TIRES

• Substitute a known good set of wheels and tires.
• Road test.
• If the vehicle still exhibits a shake or vibration, note the vehicle speed and/or engine rpm at which it occurs.

A15 VIBRATION DIAGNOSIS OF ENGINE/TRANSMISSION VS. DRIVESHAFT/SUSPENSION COMPONENTS

• Spin all four wheels independently to identify position generating problem vibration.
• For front wheels, use on-vehicle balance machine.
• For rear wheels, accelerate to half critical speed observed in road test.

A16 ROAD TEST FOR PROPER OPERATION

• After checking all wheel positions and correcting as needed, road test vehicle.

PINPOINT TEST B: TIP-IN MOAN

B1 ENGINE AIR CLEANER

• Check engine air cleaner for proper installation of base gasket, lid element and engine air cleaner intake tube and duct assembly.

B2 ENGINE MOUNTS

 
• Neutralize engine mounts as follows:
• Loosen, but do not remove, engine mount fasteners.
• Start the engine and apply service brakes.
• Shift transmission into drive and back into neutral.
• Stop engine.
• Retighten engine mounts. Road test.

B3 EXHAUST SYSTEM

 WARNING: PROPERLY VENT EXHAUST FUMES OUTSIDE OF WORKING AREA.

 WARNING: EXHAUST SYSTEM COMPONENTS ARE HOT.

• Warm up system to normal operating temperature. Loosen all hanger attachments and reposition hangers until they hang free and straight. Then loosen all flange joints and, with engine running, shift transmission from neutral to drive and back to neutral (or load engine with clutch). Tighten all hanger clamps and flanges. Road test vehicle.

PINPOINT TEST C: IDLE BOOM/SHAKE/VIBRATION

C1 CABLE/HOSES

• Check engine compartment for any component that may be grounding between the engine and body or chassis. Example: control cables, A/C hoses, accelerator cable, etc.

C2 ENGINE MOUNTS

• Inspect engine mounts.
• Neutralize engine mounts. Refer to Pinpoint Test Step B2.

C3 EXHAUST SYSTEM

 WARNING: PROPERLY VENT EXHAUST FUMES OUTSIDE OF WORK AREA.

 WARNING: EXHAUST SYSTEM COMPONENTS ARE HOT.

• Warm up system to normal operating temperature. Loosen all hanger attachments and reposition hangers until they hang free and straight. Then loosen all flange joints and, with engine running, shift transmission from neutral to drive and back to neutral (or load engine with clutch). Tighten all hanger clamps and flanges. Road test vehicle.

PINPOINT TEST D: ENGINE ACCESSORY VIBRATION

D1 ENGINE RUN-UP

• Run up engine to problem rpm observed in road test, with vehicle stationary.

D2 DRIVE BELT AND PULLEYS

• With engine stopped, inspect drive belt and pulleys for wear or damage, and check drive belt tension using Belt Tension Gauge T63L-8620-A or Rotunda Offset Belt Tension Gauge 014-R1056.
• Automatic tensioners have belt wear indicator marks. If the indicator mark is not between the min and max marks, the drive belt is worn or an incorrect drive belt is installed.

D3 MOUNTING HARDWARE

• Inspect mounting brackets and adjusting components for proper alignment and tightness.

D4 DRIVE BELT NOISE

• Check for "chirps" or squeal in drive belt by spraying a small amount of water on the grooved side of the drive belt (use a spray bottle or equivalent).

D5 DRIVE BELT AND PULLEYS — ENGINE IDLING

• With engine idling, visually check all drive belts and pulleys for misalignment, runout or irregular motion. Maximum runout is 3.175mm (0.125-inch).
• Increase engine rpm.

D6 CHECK BELT(S)

• Key off. Remove one of the drive belts.
• Key to RUN, engine running.
• If vibration still exists, remove the next drive belt. Repeat step until no drive belts are left.

PINPOINT TEST E: DRIVESHAFT VIBRATION

E1 ROAD TEST FOR VIBRATION

• Accelerate vehicle to the speed at which the customer indicated the vibration occurred.
• Record the critical vehicle speed and/or engine rpm.

E2 ROAD SPEED HOIST TEST

NOTE: On 4x4 vehicles, unlock front hubs or remove hub covers before spinning wheels.

• Raise vehicle on a frame contact hoist. Engage drivetrain and run up to observed road test speed.
• Spin non-drive wheels using an on-vehicle balance machine. Rebalance as necessary and retest.

E3 ROAD SPEED HOIST TEST WITH DRIVE WHEELS REMOVED

• Mark relative position of drive wheels on axle or hub lug and remove wheels.
• If equipped, secure brake drums with lug nuts.
• Engage drivetrain and run up to observed road test speed.

E4 DRIVESHAFT INSPECTION

• Inspect driveshaft for undercoating, physical damage, missing balance weight, improperly seated, worn or binding universal joints.

E5 CHECKING DRIVESHAFT INDEX MARKS

• Check index marks (yellow paint daubs) on rear of driveshaft and rear axle universal joint flange.

E6 DRIVESHAFT RUNOUT (ONE-PIECE DRIVESHAFT)

• With vehicle on hoist and wheels off, measure runout at front, center and rear of driveshaft with indicator, while rotating driveshaft by turning the axle.

E7 DRIVESHAFT RUNOUT (TWO-PIECE DRIVESHAFT)

• With vehicle on hoist and wheels off, measure runout at front, center and rear of driveshaft with indicator, while rotating driveshaft by turning the axle.

E8 INDEXING DRIVESHAFT AT AXLE

NOTE: With driveshaft disconnected from vehicle, manipulate universal joints in each direction of rotation. If universal joint feels stiff, lumpy or gritty in any direction, replace universal joint.

NOTE: Circular rear axle universal joint flange can be reindexed in 90-degree increments to fine tune the runout condition.

• Note or mark indexing of driveshaft to rear axle universal joint flange. Disconnect driveshaft at axle, turn 180 degrees, and reconnect.
• Recheck runout.

E9 INDEXING DRIVESHAFT AT TRANSMISSION

NOTE: WIth driveshaft removed from vehicle, manipulate universal joints in each direction of rotation. If universal joint feels stiff, lumpy or gritty in any direction, replace universal joint.

• Note or mark indexing of driveshaft at axle and transmission. Remove driveshaft, and turn 180 degrees at transmission only. Reinstall driveshaft.

E10 CHECKING REAR AXLE UNIVERSAL JOINT FLANGE FOR EXCESSIVE RUNOUT

• Compare two high points of runout marked in Steps E6 or E7 with Step E8.

PINPOINT TEST F: BRAKE VIBRATION/SHUDDER

F1 ROAD TEST FOR VIBRATION/SHUDDER

• Determine if vibration/shudder is induced when making a light stop by applying service brakes.

PINPOINT TEST G: AXLE NOISE

G1 CHECK DIFFERENTIAL LUBRICANT

• Check for low lubricant level.
• Check for wrong or poor grade axle lubricant.

G2 INSPECT AXLE HOUSING

• Check for exterior signs of damage.

G3 INSPECT CHATTER ON TURNS

• On turns, the rear axle has a chattering or groaning noise (limited slip or Traction-Lok® axles only). Slight chatter noise on slow turns after extended highway driving is considered acceptable and has no detrimental effect on the limited slip axle functions.

G4 INSPECT AXLE SHAFTS/BEARINGS

• Check axle shaft end play. Refer to the appropriate section in Group 05.
• Remove axle shafts. Inspect bearings and axle shaft journals. Refer to appropriate section in Group 05.
• Inspect axle shaft splines.
• Inspect differential gears.

G5 INSPECT RING GEAR BOLTS

• Inspect ring gear for loose or broken bolts.
• Rotate rear axle universal joint flange to view all bolts.

G6 BROKEN OR MUTILATED GEAR TEETH

• Inspect all differential gears for wear (check gear teeth for scoring abnormal wear, nicks or chips).

G7 CHECK DIFFERENTIAL BEARINGS

• Remove differential and inspect bearings for wear.

G8 INSPECT PINION GEAR/BEARINGS

• Remove pinion from axle.
• Inspect pinion and bearings for wear.

PINPOINT TEST H: NOISE AND VIBRATION — 4-WHEEL DRIVE VEHICLES

H1 INSPECT TIRES/WHEELS

• Check wheels for damage.
• Check tire pressure.
• Check tires for sawtooth wear pattern.
• Check tires for uneven inner or outer wear.
• Check tires for cupping or dishing.
• Check tire balance.

H2 INSPECT WHEEL BEARINGS

• Spin front tires by hand to check for wheel bearing roughness. Check wheel bearing end play.

H3 INSPECT LOCKING HUBS

• Inspect front hubs for wear and proper operation. Refer to Section 05-03C.

H4 CHECK TRANSFER CASE FLUID

• Remove transfer case fill plug.
• Check fluid level of transfer case.
• Check quality of transfer case fluid.

H5 INSPECT TRANSFER CASE

• Inspect transfer case for proper operation. Refer to Section 07-07 and Section 05-03C.
• Inspect internal parts for wear.

PINPOINT TEST J: DRIVESHAFT JOINT NOISE AND VIBRATION

J1 INSPECT DRIVESHAFT U-JOINTS

• Raise vehicle on hoist. Refer to Section 00-02.
• Inspect universal joints (U-joint) for excessive play (wear) between U-joint and U-joint bearing cup.

J2 INSPECT DRIVESHAFT/U-JOINTS (DRIVESHAFT REMOVED)

• Remove driveshaft and place on a suitable workbench.
• Check U-joints for seized bearing cups.
• Check U-joints for smooth rotation operation.

PINPOINT TEST K: NON-AXLE NOISE

K1 INSPECT VEHICLE TRIM

• Inspect the following for cause of noise:
• grille whistle
• trim mouldings
• roof luggage rack (if equipped)

K2 BELT SQUEAL OR CHIRP

• Check condition and tension of serpentine belt. Check other belts, if applicable.

K3 INSPECT WHEELS/TIRES

• Inspect wheels and tires. Refer to Section 04-04.

K4 INSPECT A/C SYSTEM

• Inspect A/C system components for noise when the engine is running and A/C system is alternately engaged and disengaged.

K5 EXHAUST SYSTEM

• Raise vehicle on hoist. Refer to Section 00-02.
• Check for broken or loose clamps or brackets.

K6 CHECK NON-FACTORY ACCESSORIES

• Inspect running boards, grounding body to frame, antennas, visors, bug deflectors, etc. (if equipped).