GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 GMC C Sierra - 2WD 🢒 Transmission/Transaxle 🢒 Manual Transmission - NV 3500 🢒 Transmission Clunk on Acceleration or Deceleration

Diagnostic Aids

All manual transmission 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 for the transfer case causing the clunk. Shift the transfer case into another mode. If the transmission is causing the clunk, there will not be a change.

Step

Action

Yes

No

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

1

Did you review the Symptoms - Manual Transmission, and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Manual Transmission

2

Inspect the engine mounts for being loose or damaged. Refer to Engine Mount Inspection in Engine Mechanical - 4.3L or Engine Mount Inspection in Engine Mechanical - 4.8L, 5.3L, and 6.0L.

Did you find and repair the condition?

Go to Step 10

Go to Step 3

3

Inspect the transmission mounts for being loose or damaged. Refer to Transmission Rear Mount Replacement .

Did you find and repair the condition?

Go to Step 10

Go to Step 4

4

Inspect the transmission to engine fasteners for being loose or missing. Refer to Fastener Tightening Specifications .

Did you find and repair the condition?

Go to Step 10

Go to Step 5

5

Inspect the driveline for causing the clunk. Refer to Diagnostic Starting Point - Propeller Shaft in Propeller Shaft.

Did you find and repair the condition?

Go to Step 10

Go to Step 6

6

Is the vehicle equipped with a transfer case?

Go to Step 7

Go to Step 9

7

Shift the transfer case in 4HI.

Is the clunk still present?

Go to Step 9

Go to Step 8

8

Inspect the transfer case for causing the clunk. Refer to Diagnostic Starting Point - Transfer Case in Transfer Case - NVG 236/246-NP8 (Two Speed Automatic).

Did you find and repair the condition?

Go to Step 10

Go to Step 9

9
  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission. Refer to Transmission Disassemble in Transmission Unit Repair Manual.
  3. Inspect the following transmission components that maybe causing the clunk:
    4. • The mainshaft bearing preload
    • The countershaft bearing preload
    • 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 10

Go to Diagnostic Aids

10

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1