GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Transmission/Transaxle 🢒 Manual Transmission - Medium Duty 🢒 Transmission Clunk on Acceleration or Deceleration

Diagnostic Aids

All manual transmissions have gear play that might cause a clunk. If the transmission is suspected of causing the clunk, compare it with a similar vehicle. An internal clunk in the transmission is usually caused by wear between two components, or from improper assembly, which would also cause other symptoms.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step inspects the driveline component for causing the clunk. A faulty driveline component may resonate the clunk to the transmission, giving an indication that the transmission is causing the clunk.

Step

Action

Yes

No

DEFINITION: A clunk is heard and/or felt on acceleration or deceleration.

If the transmission is equipped with an air shift control, refer to the transmission manufacturer repair manual for the correct diagnosis and repair.

1

Did you review the manual transmission symptoms and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Manual Transmission

2

Inspect the engine/transmission mounts for being loose or damaged. Refer to Engine Mount Inspection in Engine Mechanical - 8.1L or Engine Mount Inspection in Engine Mechanical - 7.2L Caterpillar or Transmission Support Replacement or Transmission Mount Bracket Replacement or Transmission Mount Replacement .

Did you find and repair the condition?

Go to Step 8

Go to Step 3

3

Inspect the transmission to engine fasteners for being loose or missing. Refer to Clutch Assembly Replacement in Clutch.

Did you find and repair the condition?

Go to Step 8

Go to Step 4

4

Inspect the driveline for causing the clunk. Refer to Ping, Snap, or Click Noise in Propeller Shaft.

Did you find and repair the condition?

Go to Step 8

Go to Step 5

5

Inspect for loose propeller shaft yoke.

Is the propeller shaft yoke loose?

Go to Step 6

Go to Step 7

6

Replace the propeller shaft yoke, washer, and nut. Refer to the transmission manufacturer repair manual.

Did you find and repair the condition?

Go to Step 8

Go to Step 7

7
  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission.

    3. Refer to the transmission manufacturer repair manual.

  3. Inspect the following transmission components that maybe causing the clunk:
    4. • The mainshaft bearing end play
    • The countershaft bearing end play
    • Worn speed gear teeth
    • Worn countershaft gear teeth
    • Worn synchronizer sleeve to hub
    • Worn thrust washers and thrust surfaces on the speed gears or mainshaft

Did you find and repair the condition?

Go to Step 8

Go to Diagnostic Aids

8

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1