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Home >> GMC >> 2018 >> Acadia Denali, FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 198 (Manual Transmission - TREMEC 6-Speed (M3L Mg9)) >> Diagnostic Information and Procedures >> Transmission Clunk on Acceleration or Deceleration (MG9) >> Test Description

Test Description

WARNING: This page is about a different car, the 2017 Cadillac ATS. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 5 

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

Step Action Yes No
DEFINITION: A clunk is heard and/or felt on acceleration or deceleration.
1 Did you review the Symptoms - Manual Transmission (MG9)  and perform the necessary inspections? Go to Step 2  Go to Symptoms - Manual Transmission (MG9) 
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 transmission mounts for being loose or damaged. Refer to Transmission Mount Inspection .
Did you find and repair the condition?
Go to Step 7  Go to Step 4 
4 Inspect the transmission to engine fasteners for being loose or missing. Refer to Fastener Specifications (On Vehicle) Fastener Specifications (MG9) .
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 Symptoms - Propeller Shaft .
Did you find and repair the condition?
Go to Step 7  Go to Step 6 
6
  1. Remove the transmission. Refer to Transmission Replacement (MG9) .
  2. Disassemble the transmission. Refer to Transmission Disassemble (MG9) .
  3. Inspect the following transmission components that maybe causing the clunk:
    • Faulty mainshaft bearings
    • Faulty counter gear shaft bearings
    • Worn speed gear teeth
    • Worn counter gear shaft 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