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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 938 (Manual Transmission -- NV 4500) >> Diagnostic Information and Procedures >> Transmission Clunk on Acceleration or Deceleration >> Test Description

Test Description

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

  1. 8:  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.
Transmission Clunk on Acceleration or Deceleration

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 toSymptoms - Manual Transmission 
2 Inspect the engine mounts for being loose or damaged. Refer to 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 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 10 
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) or Diagnostic Starting Point - Transfer Case in Transfer Case - NVG 261-NP2 (Two Speed Manual).
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 article.
  3. Inspect the following transmission components that maybe causing the clunk:
    • 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 
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