Inspection and Verification

Tire Wear

1. Inspect tires for wear. The original equipment tires have built-in tread wear indicators to show when tires need replacement. Abnormal or excessive wear may be caused by incorrect wheel alignment, wheel/tire imbalance or improper tire pressure. Refer to Section 04-04.

2. NOTE: Tires which show irregularities and definite roughness must be replaced.

   Inspect to determine if the following conditions apply:

   
   
   

   VISUAL INSPECTION CHART

   Mechanical
   incorrect mounting misalignment loose wheel bearings bent wheels cupping or scalloping of tires from imbalance possible loose or worn steering connecting rod, drag link and pitman arm underinflation and/or mechanical irregularities such as out-of-balance condition of wheel and/or tire and bent or damaged wheel loose, damaged or worn front suspension parts

   
   
   
   Tire Wear
   
   
   
   
   

Vibration and Roughness

Vibration, roughness, tramp, shimmy and thump may be caused by excessive tire or wheel runout, worn or cupped tires, or wheel and tire imbalance.

These conditions may also be caused by rough or undulating road surfaces. Driving the vehicle on different types of road surfaces will indicate if the road surfaces are actually causing the condition.

Do not immediately suspect the tires when attempting to diagnose a vibration concern. Other sources of vibration include:

• loose or worn wheel bearings
• loose or worn suspension or steering components
• brake hub and rotor or drum runout
• loose engine or transmission supports
• engine driven accessories

This section covers those vibrations related to the tires and wheels.

For diagnostic procedures and service for non-tire related vibrations, refer to Section 00-04.

Road Test

A tire vibration diagnostic procedure always begins with a road test. The road test and customer interview (if available) will provide much of the information needed to find the source of a vibration.

During the road test, drive the vehicle on a road that is smooth and free of undulations. If vibration is apparent, note and record the following:

• the speed at which the vibration occurs
• what type of vibration occurs in each speed range — mechanical (such as shake) or audible (such as tire whine)
• how the vibration is affected by changes in vehicle speed, engine speed, and engine torque
• type of vibration sensitivity — torque sensitive, vehicle speed sensitive, or engine speed sensitive

If the road test indicates the vibration is related to the tires or wheels, refer to Pinpoint Test G in this section. Refer to Section 04-04 to help pinpoint the cause of the concern. If the road test indicates there is tire whine, but no shake or vibration, the noise originates with the contact between the tire and the road surface.

• A thumping noise usually means the tire has flat or soft spots making a noise as they slap the roadway. Tire whine can be distinguished from axle noise because axle noise diminishes or changes according to load or speed. Tire noise remains the same over a range of speeds.
• To verify that tire noise is not associated with shake or vibration, inflate the tires one at a time and check for a change in the sound. The pitch or whine will change as the increased pressure changes the tire frequency.
• Be sure to deflate tires to their proper pressures after this check is completed.
• A complete road test procedure is provided in Section 00-04.

Use the following explanation of terms to help isolate the source of the vibration.

Torque Sensitive

The condition can be improved or worsened by accelerating, decelerating, coasting, maintaining a steady vehicle speed and application of engine torque.

Vehicle Speed Sensitive

The vibration always occurs at the same vehicle speed and is not affected by engine torque, engine speed, or transmission (7003) gear selection.

Engine Speed Sensitive

The vibration occurs at varying vehicle speeds when a different transmission gear is selected. It can sometimes be isolated by increasing or decreasing engine speed with the transmission in NEUTRAL, or by stall testing with the transmission in gear. If the condition is engine-speed sensitive, the condition is not related to tires.

Front End

1.  CAUTION: Do not attempt to adjust front wheel alignment without making a preliminary inspection of the front end parts, and correcting where necessary.

   Fill all fluids to specification.

2. Make sure spare tire or wheel and related equipment are properly stored.

3. Remove any excessive accumulation of mud, dirt or road deposits from the chassis and underbody.

4. Retain all normal loads in the vehicle. Inflate all tires to the pressure specified on the Safety Compliance Certification Label (usually located on the inside driver's door pillar).

5. Check both front tires and make sure they are the same size, ply rating, and load range.

6. Inflate all tires to specified pressure (cold). Check both front tires for the same size, ply rating and load range. Refer to Section 04-04.

7. Check for excessive front wheel bearing end play. Refer to Wheel Bearings, Front, in the Adjustments portion of this section. Adjust and/or replace the front wheel bearings. Refer to Section 04-01A or Section 04-01B.

8. Check for worn or damaged spindle pins (kingpins) or ball joints. Replace the ball joints or spindle pins (kingpins). Refer to Section 04-01A (4x2) and Section 05-03A or Section 05-03B.

9. Check for bent steering linkage or excessively worn joints. Refer to Section 11-03.

10. Check the steering gear mounting bolts and tighten to the specified torque. Refer to Section 11-02B or Section 11-02D.

11. Inspect the radius arm if bent or damaged. Inspect the bushings at the radius arm-to-frame attachment for wear and looseness. Repair or replace parts as required. Refer to Section 04-01A or Section 04-01B.

12. Check other suspension components for damage.

13. Check for aftermarket changes to steering, suspension, wheel and tire components (i.e., competition, heavy-duty, etc.). Specifications in this manual do not apply to vehicles with aftermarket changes.

Ball Joint, Upper, Inspection

Refer to Ball Joints, Front Suspension Upper Arm and Lower, Twin I-Beam Front Axle Equipped with Joints, under Component Tests in the Diagnosis and Testing portion of this section.

Refer to Section 04-01A for service to ball joint assembly on 4x2 vehicles. For 4x4 vehicles, refer to Section 05-03A or Section 05-03B.

Ball Joint, Lower, Inspection

Refer to Ball Joints, Front Suspension Upper Arm and Lower, Twin I-Beam Front Axle Equipped with Joints, under Component Tests in the Diagnosis and Testing portion of this section.

Refer to Section 04-01A for service to ball joint assembly on 4x2 vehicles. For 4x4 vehicles, refer to Section 05-03A or Section 05-03B.

Shock Absorber Checks

 CAUTION: The low pressure gas shock absorbers are charged with nitrogen gas to 931 kPa (135 psi) for 1 inch and 1-3/16 inch bore, and 1034 kPa (150 psi) for 1-3/8 inch bore. Do not attempt to open, puncture or apply heat to the shock absorbers.

All vehicles are equipped with low pressure gas-filled hydraulic shock absorbers of the direct acting type. They are non-adjustable and non-refillable. They cannot be serviced as cartridges and must be serviced as shock assemblies.

Before replacing a shock absorber, check the action of the shock absorbers as follows.

Vehicle Inspection

1. Check all tires for proper inflation pressure.

2. Check tire condition to confirm proper front end alignment, tire balance and overall tire condition such as separation or bulges.

3. Check the vehicle for optional suspension equipment such as heavy-duty handling or trailer tow suspensions. These suspensions will have a firmer ride feeling than standard suspensions.

4. Check the vehicle attitude for evidence of possible overload or sagging.

   Many times front springs and front shock absorbers (18124) are replaced in an effort to solve a vehicle sag concern. Shock absorbers are, by design, hydraulic damping units only, and unlike suspension springs, do not support any suspension loads. Therefore, replacing a shock absorber will not correct a vehicle sag concern.

5. Road test vehicle to confirm customer concern.

6. Make sure the shock absorber is securely and properly installed.

7. Check the shock absorber insulators for damage and wear.

8. Replace any worn or damaged insulators and tighten attachments to the specified torque (on a shock absorber which incorporates internal insulators, replace the shock absorbers).

9. Tighten shock absorber attachments to 34-47 Nm (25-35 lb-ft) upper, 60-81 Nm (45-60 lb-ft) lower.

10. Inspect the shock absorber for evidence of fluid leakage.

    A light film of oil (weepage) on the upper portion of the front shock absorber is permissible and is a result of proper shock lubrication. Weepage is a condition in which a thin film of oil may be deposited on the shock outer tube (body) and is normally noticed due to the collection of dust in this area. Front shock absorbers which exhibit this weepage condition are functional units and should not be replaced. Leakage is a condition in which the entire shock body is covered with oil and the oil will drip from the shock onto the pavement.

11. If leakage exists:

    1. Make sure the fluid observed is not from sources other than the front shock absorber.
    2. Replace the worn or damaged front shock absorber.

12. Disconnect the lower end of the shock absorber.

13. Extend and compress the shock absorber as fast as possible, using as much travel as possible. Action should be smooth and uniform throughout each stroke.

    • Higher resistance on extension than on compression is a normal condition.
    • Faint swish noises are also normal.
    • Make sure the part number of the replacement is the same as that of the original shock absorber.

Hoist Check

1. Noise: Noise can be caused by loose suspension or shock attachments. Verify that all attachments or the suspension components and front springs and front shock absorbers are tight. Replace any worn or damaged upper stud insulators. Check front springs and front shock absorbers for external damage.

2. Bottom/Hopping: Check condition of the rubber suspension travel stops (front suspension bumpers (3020)). Replace if worn or missing. Examine for evidence of previous overload or damaged components.

3. Force-Check: Support axle and remove lower front shock attachment. Stroke front shock body using as much travel as possible. The action should be smooth and uniform throughout each stroke. Damping forces should be equivalent on both sides of the vehicle.

4. Replace only the worn or damaged front shock absorber.

   In the past it was recommended that front shock absorbers be replaced in pairs if one unit became unserviceable. Improved sealing, new materials, design and improved rod machining and hardening techniques have added to the reliability of shock absorbers. Therefore, front shock absorbers no longer need to be replaced in pairs when only one unit is not serviceable.

Bench Test

The front shock absorbers are gas-pressurized, which results in their being fully extended when not restrained. If a front shock absorber does not fully extend, it is damaged and should be replaced. Check length overall (LOA). If the front shock absorber does not meet the length overall requirement, it is a good indication something internal is not to specification and the front shock absorber should be replaced.

With the front shock absorber in the normal upright position, compress it and allow it to extend three times to purge the pressure chamber of any gas that may have been introduced during handling.

Place the front shock absorber right side up in a vise. Hand-stroke the front shock absorber as fast as possible using as much travel as possible. Action should be smooth and uniform throughout each stroke. Higher resistance on extension than on compression is normal.

The following conditions are abnormal:

• A lag or skip at reversal of travel near mid-stroke when front shock absorber is properly primed and in the installed position
• Seizing
• Noise, other than a faint swish, such as a clicking upon fast stroke reversal
• Excessive fluid leakage
• With rod fully extended, any lateral motion of rod in relation to outer cylinder

If front shock absorber action remains erratic after purging air, install a front shock absorber, replacing only the damaged front shock absorber. Front shock absorbers do not need to be replaced as sets.

Suspension, Rear

1. Check for leaks on shock absorbers (18080).

2. Check shock absorber operation for stiff, rough or spongy operation.

3. Check condition or rear suspension bushings and rear suspension springs.

If the above checks reveal evidence of excessive wear, deterioration, or improper operation, replace damaged components.

Vehicle Lean

Side-to-side vehicle lean should be verified by measuring the fender lip-to-ground dimension before beginning diagnosis and service actions. Normal acceptable limits are:

• Maximum of 16mm (5/8-inch) variance between left and right front wheel lips to ground.
• Maximum of 19mm (3/4-inch) variance between left and right rear wheel lips to ground.

NOTE: Codes identifying the front and rear spring options and springs are printed on the Safety Standard Certification Label. Replace springs in pairs if one is found to be damaged or worn. If a spring should require replacement because it is damaged, worn or due to a leaning condition, replace only with the same part specified on the label. In rare instances, the spring codes will not reflect the springs as installed due to a DSO option or assembly plant substitution. If a DSO option number is shown on the certification label, the District Office can establish whether springs are affected. If the factory-installed springs do not agree with the code printed on the Safety Standard Certification Label (right and left spring part number should match), replace the damaged or worn spring with a new spring of the same part number as the damaged or worn spring. It will not be necessary to replace the matching, non-worn or undamaged spring.

1. Place the vehicle on a flat, smooth surface.

2. Inspect vehicle for any heavy add-ons that may cause excessive weight on any corner of the vehicle.

   • In cases where the excess weight is a snow plow, a rear tailgate lift, etc., the vehicle must be diagnosed with the equipment in place.
   • Measure corner weights if necessary.
   • Vehicle should be empty, fuel tanks full, no cargo such as tools, equipment or debris in the pickup box or rear body section.
   • Vehicle must be sitting on the wheels and tires and not a hoist, jack or jack stands.

3. Check all wheels (1007) and tires:

   • Wheels must be same size and design, right and left side on each axle.
   • Wheels size and design, tire size and tire design should be as indicated on the Vehicle Certification Label.
   • Check air pressure of all tires; inflate to specifications indicated on the Vehicle Certification Label.

4. Check front and rear suspension. Make sure the same spring is on the left/right front and left/right rear. The front springs have I.D. tags indicating the part number. The rear springs (5560) have the part number stamped on the bottom just behind the U-bolt attachment.

5. Jounce the vehicle's front and rear suspension to normalize the vehicle static ride height.

6. Measure the height of the right and left fender lip openings for both front (dimension A) and rear (dimension B).

7. Calculate the side-to-side differences for each dimension. If these differences are greater than 16mm (5/8 inch) between left or right front and/or 19mm (3/4 inch) between left and right rear, adjustment can be performed following the Vehicle Lean Correction procedure under Adjustments in this section.