GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2009 🢒 Cobalt 🢒 Transmission 🢒 Manual Transmission - M86 🢒 Transmission Clunk on Acceleration or Deceleration

Diagnostic Aids

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

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step inspects the driveline components that may be the cause of the clunk noise. The noise may resonate to the transaxle.

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.

Did you find and repair the condition?

Go to Step 7

Go to Step 3

3

Inspect the transaxle mounts for being loose or damaged. Refer to Transmission Rear Mount Replacement or Transmission Mount Replacement - Left Side.

Did you find and repair the condition?

Go to Step 7

Go to Step 4

4

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

Did you find and repair the condition?

Go to Step 7

Go to Step 5

5

Inspect the driveline for causing the clunk. Refer to Clunk When Accelerating from Coast.

Did you find and repair the condition?

Go to Step 7

Go to Step 6

6
  1. Remove the transaxle. Refer to Transmission Replacement.
  2. Disassemble the transaxle. Refer to Transmission Case Disassemble.
  3. Inspect the following transaxle components that maybe causing the clunk:
    4. • Faulty mainshaft bearings
    • Faulty countershaft bearings
    • 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 7

Go to Diagnostic Aids

7

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1