GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Transmission/Transaxle 🢒 Manual Transmission - ZF S6-650 🢒 Transmission Noisy

Diagnostic Aids

If the transmission is in neutral with the engine operating, and a whirling 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 causing a vibration. The vibration may be 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 noise may be a whine or a growl caused by faulty bearings or gears. The noise may also be caused from a faulty component causing a vibration noise.

1

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

Go to Step 2

Go to Symptoms - Manual Transmission

2

Is the noise present while in neutral, with the engine operating?

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 Vibration Analysis - Driveline in Vibration Diagnosis and Correction.

Did you find and repair the condition?

Go to Step 22

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 21

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 22

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 of fluid. Refer to Transmission Fluid Replacement .

Did you find and repair the condition?

Go to Step 22

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 Control Lever and/or Boot Replacement .

Did you find and repair the condition?

Go to Step 22

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 causing 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 20

Go to Step 16

16

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

Is the noise still present?

Go to Step 17

Go to Step 20

17

Inspect for engine to transmission alignment and loose transmission mounting bolts.

Are there any loose transmission mounting bolts?

Go to Step 18

Go to Step 21

18

Notice: Refer to Fastener Notice in the Preface section.

Replace and tighten the transmission mounting bolts. Refer to Fastener Tightening Specifications .

Is the noise still present?

Go to Step 19

Go to Step 22

19

With the engine operating, depress the clutch pedal.

Is the noise still present?

Go to Step 20

Go to Step 21

20
  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 22

Go to Step 21

21

  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission. Refer to Transmission Disassemble . 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 22

--

22

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1