GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Electrical 🢒 Transmission Noisy

Diagnostic Aids

If the vehicle is equipped with the 8.1L engine, the transmission is in neutral with the engine operating, and a whirling kind of a noise, neutral gear rattle, is heard outside the vehicle, this is a normal condition.

Test Description

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

  1. This step inspects for vibration causing a noise. If the vehicle is equipped with an aftermarket box or is carrying a certain load, the driveline axle may not be correct, and could cause a vibration. The vibration maybe resonating into the transmission, causing a noise.

    2.

  2. This step inspects for the correct transmission fluid level. If the transmission fluid level is excessively low, damage may have occurred to the transmission components.

  3. This step inspects for the correct type of transmission fluid. The transmission uses a special fluid. If the incorrect fluid was used, there may have been an overheating condition. Overheating may cause damage to the transmission components.

    4.

  4. This step inspects for noise coming into the driver compartment. Improper sealing of the shift tower may be allowing normal transmission noise to be heard by the driver.

    5.

  5. This step tests to determine if clutch components are making the noise. Depress the clutch pedal slowly and listen for the change in noise. If the noise changes while pressing the pedal, it may be a faulty clutch component. If the noise does not change until the clutch is completely disengaged, the transmission component is faulty.

Step

Action

Yes

No

DEFINITION: The transmission is making a noise. The different noises may be a whine or a growl caused by faulty bearings or gears. The noise may also be caused by a faulty component, causing a vibration noise or rattle.

1

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

Go to Step 2

Go to Symptoms - Manual Transmission

2

If the vehicle is equipped with an 8.1L, is the noise present while in neutral?

Go to Diagnostic Aids

Go to Step 3

3

Is the noise present at a certain road speed or with a certain load?

Go to Step 4

Go to Step 5

4

Inspect for the correct driveline angle. Refer to Driveline Working Angles Measurement in Vibration Diagnosis and Correction.

Did you find and repair the condition?

Go to Step 24

Go to Step 5

5

Is the noise present in all gears?

Go to Step 7

Go to Step 6

6

Is the noise present in just one gear?

Go to Step 23

Go to Step 7

7

Inspect the transmission fluid level.

Is the fluid level correct?

Go to Step 9

Go to Step 8

8

Add transmission fluid. Refer to Transmission Fluid Replacement .

Did you find and repair the condition?

Go to Step 24

Go to Step 9

9

Inspect the transmission for the correct fluid type. Refer to Lubrication Specifications .

Is the transmission fluid the correct type?

Go to Step 11

Go to Step 10

10

Drain and fill the transmission with the correct type fluid. Refer to Transmission Fluid Replacement .

Did you find and repair the condition?

Go to Step 24

Go to Step 11

11

Inspect the shift tower boot.

Is the closeout boot loose or damaged?

Go to Step 12

Go to Step 13

12

Position and tighten the shift tower boot to specifications. Refer to Fastener Tightening Specifications .

Did you find and repair the condition?

Go to Step 24

Go to Step 13

13

Is the vehicle equipped with a power take off (PTO)?

Go to Step 14

Go to Step 17

14

Remove the PTO in order to confirm that the PTO is not the cause of the noise.

Is the noise still present?

Go to Step 17

Go to Step 15

15

Inspect the countershaft gear for damage from the PTO.

Is the countershaft gear damaged?

Go to Step 23

Go to Step 16

16

Install the PTO. Ensure it is properly shimmed. Refer to the PTO manufactures installation procedure.

Is the noise still present?

Go to Step 17

Go to Step 24

17

Is the vehicle equipped with a transfer case?

Go to Step 18

Go to Step 19

18

Engage the transfer case in the different modes.

Is the noise still present or the same?

Go to Step 19

Go to Symptoms - Transfer Case in Transfer Case NVG 236/246-NP8 or Symptoms - Transfer Case in Transfer Case NVG 261-NP2

19
  1. Inspect for engine to transmission alignment.
  2. Inspect for loose transmission mounting bolts.

Are there any loose transmission mounting bolts?

Go to Step 20

Go to Step 21

20

Replace and tighten the transmission mounting bolts. Refer to Transmission Mount Replacement .

Is the noise still present?

Go to Step 21

Go to Step 24

21

With the engine operating, depress the clutch pedal.

Is the noise still present?

Go to Step 22

Go to Step 23

22
  1. Remove the clutch. Refer to Clutch Assembly Replacement in Clutch.
  2. Inspect the following components for being the cause of the noise.
    3. • The release bearing
    • The pilot bearing
    • The dual mass flywheel, if equipped
    • The pressure plate
    • The clutch disc
    • The input shaft bearing
    • The engine crankshaft end play

Did you find and repair the condition?

Go to Step 24

Go to Step 23

23

  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission. Refer to Transmission Disassemble in Manual Transmission - ZF S6-650 Unit Repair. Use the information in the Cleaning and Inspection section to determine if any of the transmission components are faulty.

Did you find and repair the condition?

Go to Step 24

--

24

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1