Have you performed the Vibration Analysis - Road Testing table?

Go to Step 2

Go to Vibration Analysis - Road Testing

2

1. Operate the vehicle at the speed of the vibration concern.
2. While maintaining the concern speed, drive the vehicle through slow, sweeping turns - first in one direction, then in the other direction.
3. Observe the vehicle for changes in the vibration disturbance.
4. Select a smooth, level surface, such as an empty parking lot or a remote road.
5. While maintaining the vehicle at the concern speed if possible, drive the vehicle through sharp turns (360 degrees) - first in one direction, then in the other direction.
6. Observe the vehicle for changes in the vibration disturbance.

Did the characteristics of the vibration change significantly (become worse or go away) during these steps?

Go to Step 3

Go to Step 6

Did you hear a growling noise during these steps?

Go to Step 5

Go to Step 4

4

1. With the vehicle at a stand-still, apply the regular brake and place the transmission in the lowest forward gear.

Important: Do not accelerate to the point of causing the drive wheels to squeal, slip or hop - this would obscure the results of the test.

2. Release the regular brakes and accelerate aggressively to 32 km/h (20 mph).
3. Observe the vehicle for changes in the vibration disturbance.

Did you feel a shudder or shaking during these steps?

Go to Step 6

Go to Vibration Diagnostic Aids

5

1. Inspect the wheel bearings for wear and/or damage. Refer to Wheel Bearings Diagnosis.
2. Replace any of the wheel bearings found to be worn and/or damaged. Refer to the appropriate procedure:

•	Front Wheel Hub, Bearing, and Seal Replacement

•	Rear Axle Hub, Bearing, Cup, and/or Seal Replacement

Did you find and correct a condition?

Go to Step 9

Go to Vibration Diagnostic Aids

6

1. Inspect the following suspension components for wear, damage, looseness and/or possible contact with other vehicle components:

•	Shock absorbers

•

Springs

•

Bushings

•	Insulators

•	Equalizing beams

•	Torque rods

•	Steering knuckles

•

King pins

2. Replace any of the suspension components found to be worn, damaged, loose and/or contacting other vehicle components.

Did you find and correct a condition?

Go to Step 9

Go to Step 7

7

1. Inspect the powertrain mounts for the following:

•	Loose and/or missing fasteners

•	Improper alignment

•	Cracked, dry-rotted, and/or oil-soaked insulators

•	Twisted, broken, torn, and/or collapsed insulators

•	Bent, twisted, and/or deformed brackets

2. Replace powertrain mounts as necessary. Refer to the following procedures:

•	Engine Front Mount Replacement

•	Engine Rear Mount Replacement

•	Transmission Mount Replacement for the medium duty transmission

•	Transmission Support Replacement for the Allison transmission

3. Inspect the exhaust system components for the following:

•	Loose and/or missing fasteners

-	Heat shields

-	Joints and/or couplings-nuts, bolts, studs, clamps, straps

-

-	Bracket and/or insulator mounting

•	Inadequate clearance to body and/or chassis components (with the exhaust system both COLD and HOT; in NEUTRAL, FORWARD and REVERSE gears)

•	Improper alignment

•	Disconnected and/or missing insulators

•	Cracked, dry-rotted, and/or oil-soaked insulators

•	Stretched, twisted, broken, torn, and/or collapsed insulators

•	Bent, twisted, cracked, and/or deformed brackets

4. Repair, replace, and/or realign exhaust system components as necessary.

Did you find and correct a condition?

Go to Step 9

Go to Step 8

8

Inspect the vehicle trim height and adjust as necessary. Refer to Trim Height Inspection.

Did you find and correct a condition?

Go to Step 9

Go to Vibration Diagnostic Aids

1. Install or connect any components that were removed or disconnected during diagnosis.
2. Perform the Vibration Analysis - Road Testing table. Refer to Vibration Analysis - Road Testing .

Is the vibration still present?

Go to Step 2

System OK