GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Cobalt 🢒 Transmission/Transaxle 🢒 Manual Transaxle - MU3 🢒 Transmission Fluid Leak Diagnosis

Diagnostic Aids

Using the incorrect type of transaxle fluid may affect the sealing ability of the seals. Ensure the use of the correct type of transaxle fluid. The incorrect type of sealer may not be compatible with the transaxle fluid or may not have the correct characteristics for sealing the affected components. Ensure the use of the correct type of sealers. Refer to Adhesives, Fluids, Lubricants, and Sealers in Manual Transaxle MU3 - Unit Repair.

Test Description

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

  1. Use an approved method to clean the transaxle to ensure the leak location is correctly identified. If using a powder method or dye method, ensure the products are compatible with the transaxle fluid.

Step

Action

Yes

No

DEFINITION: Visible sign of the transaxle fluid leaking from the transaxle.

1

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

Go to Step 2

Go to Symptoms - Manual Transmission

2
  1. Inspect for the transaxle fluid level higher than the recommended level. Refer to Transmission Fluid Replacement .
  2. Adjust the transaxle fluid level if incorrect.

Was the transaxle fluid level too high?

Go to Step 23

Go to Step 3

3

Inspect the transaxle vent for a blockage.

Is the transaxle vent blocked?

Go to Step 4

Go to Step 5

4

Repair or replace the transaxle vent.

Did you find and repair the condition?

Go to Step 23

Go to Step 5

5

Verify the location of the leak.

  1. Clean the transaxle assembly.
  2. Operate the vehicle for 24 km (15 mi), or until normal operating temperatures are reached.
  3. Visual inspect or use the powder method or dye and black light method to locate the leak.

Is the leak occurring at the drain or fill plug?

Go to Step 6

Go to Step 7

6

Replace the drain or fill plug. Refer to Transmission Fluid Replacement .

Did you find and repair the condition?

Go to Step 23

Go to Diagnostic Aids

7

Is the leak at the transaxle output shaft seal?

Go to Step 8

Go to Step 9

8

Remove the axle seal and inspect for the following:

    • Damaged or worn seal
    • Damaged seal bore
    • Improper installation
    • Cracks in the component
    • Loose or worn bearing causing excessive seal wear

Refer to Axle Seals Replacement .

Did you find and repair the condition?

Go to Step 23

Go to Diagnostic Aids

9

Is the leak at the shift lever area?

Go to Step 10

Go to Step 11

10
  1. Inspect the shift control lever lower boot for damage.
  2. Inspect for loose shift control lever mounting bolts.
  3. Remove the shift control lever. Refer to Shift Control Assembly Replacement .
  4. Replace the shift control lever lower boot if damaged.
  5. Inspect the shift control lever sealing surfaces for scratches, nicks or damage.

Did you find and repair the condition?

Go to Step 23

Go to Diagnostic Aids

11

Is the leak at the front of the transaxle?

Go to Step 12

Go to Step 14

12
  1. Inspect for the leak at the input shaft seal.
  2. Inspect for the following if the input shaft seal is leaking:
    3. • Damaged or worn seal
    • Damaged seal bore
    • Improper installation
    • Cracks in the component
    • Input shaft sealing surface is scratched, nicked, damaged or worn
    • Loose or worn bearing causing excessive seal wear
  3. Replace the input shaft seal if leaking. Refer to Transmission Disassemble in Manual Transmission MU3 - Unit Repair.

Did you find and repair the condition?

Go to Step 23

Go to Step 13

13
  1. Inspect the case for cracks or porosity.
  2. Replace the transaxle case or clutch housing if it is faulty. Refer to Transmission Disassemble in Manual Transmission MU3 - Unit Repair.

Did you find and repair the condition?

Go to Step 23

Go to Diagnostic Aids

14

Is the leak at the vehicle speed sensor (VSS)?

Go to Step 15

Go to Step 16

15
  1. Remove the VSS.
  2. Inspect for the following:
    3. • Cut or damaged O-ring seal
    • VSS over-tightened causing deformation in the VSS
    • VSS bore scratched or damaged

Did you find and repair the condition?

Go to Step 23

Go to Step 1

16

Is the leak at the backup lamp switch?

Go to Step 17

Go to Step 19

17
  1. Remove the backup lamp switch.
  2. Inspect for the following:
    3. • Cross threaded or damaged threads
    • Insufficient sealant
    • Leaking switch
    • Improper installation

Did you find and repair the condition?

Go to Step 23

Go to Step 1

18
  1. Remove the shift shaft detent sleeve. Refer to Transmission Disassemble in Manual Transmission MU3 - Unit Repair and Transmission Case Assemble in Manual Transmission MU3 - Unit Repair.
  2. Inspect for the following:
    3. • Cross threaded or damaged threads
    • Insufficient sealant
    • Cracked sleeve or case
    • Improper installation

Did you find and repair the condition?

Go to Step 23

Go to Step 1

19

Is the leak at the sealing flanges of the transaxle case?

Go to Step 20

Go to Step 21

20
  1. Remove the transaxle. Refer to Transmission Replacement .
  2. Disassemble the transaxle. Refer to Transmission Disassemble in Manual Transmission MU3 - Unit Repair.
  3. Inspect the sealing surfaces. Refer to Clutch and Differential Housing Cleaning and Inspection in Manual Transmission - Unit Repair.

Did you find and repair the condition?

Go to Step 23

Go to Step 21

21

Is the leak coming from a crack or porosity in the transaxle case?

Go to Step 22

Go to Diagnostic Aids

22
  1. Remove the transaxle. Refer to Transmission Replacement .
  2. Disassemble the transaxle. Refer to Transmission Disassemble in Manual Transmission MU3 - Unit Repair.
  3. Replace the faulty transaxle case or clutch housing. Refer to Transmission Case Assemble in Manual Transmission MU3 - Unit Repair .

Did you find and repair the condition?

Go to Step 23

Go to Diagnostic Aids

23

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 1