GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Transmission 🢒 Manual Transmission - Medium Duty 🢒 Transmission Noisy

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 vibration occurs at a certain road speed , or carrying a certain load, the driveline axle may not be correct, and possibly 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 overheating. Overheating may cause damage to the transmission components.

    4.

  4. 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 from faulty bearings or gears. The noise may also be caused from a faulty component, causing a vibration noise.

If the transmission is equipped with an air shift control, refer to the transmission manufacturer repair manual for the correct diagnosis and repair.

1

Did you review the manual transmission symptom operations and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Manual Transmission

2

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

Go to Step 3

Go to Step 4

3

Inspect for the correct driveline angle. Refer to Vibration Analysis - Driveline .

Did you find and repair the condition?

Go to Step 19

Go to Step 4

4

Is the noise present in all gears?

Go to Step 6

Go to Step 5

5

Is the noise present in just one gear?

Go to Step 18

Go to Step 6

6

Inspect the transmission fluid level.

Is the fluid level correct?

Go to Step 8

Go to Step 7

7

Add transmission fluid. Refer to the transmission manufacturer repair manual.

Did you find and repair the condition?

Go to Step 19

Go to Step 8

8

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

Is the transmission fluid the correct type?

Go to Step 10

Go to Step 9

9

Drain and refill the transmission with the correct type fluid. Refer to the transmission manufacturer repair manual.

Did you find and repair the condition?

Go to Step 19

Go to Step 10

10

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

Go to Step 11

Go to Step 14

11

Remove the PTO, in order to confirm that the PTO is not causing the noise.

Is the noise still present?

Go to Step 14

Go to Step 12

12

Inspect the countershaft gear for damage from the PTO.

Is the countershaft gear damaged?

Go to Step 18

Go to Step 13

13

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

Is the noise still present?

Go to Step 14

Go to Step 19

14

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

Are there any loose transmission mounting bolts?

Go to Step 15

Go to Step 16

15

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

Is the noise still present?

Go to Step 16

Go to Step 19

16

With the engine operating, depress the clutch pedal.

Is the noise still present?

Go to Step 17

Go to Step 18

17

  1. Remove the clutch. Refer to Clutch Assembly Replacement .
  2. Inspect the following components for being the cause of the noise.
    3. • The release bearing
    • The pilot bearing
    • 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 19

Go to Step 18

18

  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission. Refer to the transmission manufacturer repair manual to determine if any of the transmission components are faulty.

Did you find and repair the condition?

Go to Step 19

--

19

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1