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Home >> GMC >> 2006 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1159 (Manual Transmission - AISIN AY6) >> Diagnostic Information and Procedures >> Transmission Fluid Leak Diagnosis >> Test Description

Test Description

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 5:  Use an approved method to clean the transmission to ensure the leak location is correctly identified. If using a powder method or dye method ensure the products are compatible with the transmission fluid.
Step Action Yes No
DEFINITION: Visible sign of the transmission fluid leaking from the transmission.
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 transmission fluid level higher than the recommended level. Refer to Transmission Fluid Level Inspection .
  2. Adjust the transmission level if incorrect.
Was the transmission fluid level too high?		 Go to Step 25  Go to Step 3 
3 Inspect the transmission vent for a blockage.
Is the transmission vent blocked?		 Go to Step 4  Go to Step 5 
4 Repair or replace the transmission vent.
Did you find and repair the condition?		 Go to Step 25  Go to Step 5 
5  Verify the location of the leak.
  1. Clean the transmission 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 25  Go to Diagnostic Aids
7 Is the leak at the transmission output shaft seal? Go to Step 8  Go to Step 9 
8 Remove the mainshaft rear oil seal and inspect for the following. Refer to Mainshaft Rear Oil Seal Replacement .
  • Damaged or worn seal
  • Damaged seal bore
  • Improper installation
  • Cracks in the component
  • Output flange sealing surface is scratched, nicked, damaged, or worn
  • Loose or worn bearing causing excessive seal wear
  • Output flange nut loose

Did you find and repair the condition?		 Go to Step 25  Go to Diagnostic Aids
9 Is the leak at the shift rail area? Go to Step 10  Go to Step 11 
10 Inspect the shift rail seal for damage.
Did you find and repair the condition?		 Go to Step 25  Go to Diagnostic Aids
11 Is the leak at the front of the transmission? Go to Step 12  Go to Step 15 
12
  1. Remove the transmission. Refer to Transmission Replacement .
  2. Inspect the input shaft for leaking.
  3. Remove the CSC assembly. Refer to Clutch Concentric Actuator Cylinder Replacement (CTS) .
Did you find and repair the condition?		 Go to Step 25  Go to Step 13 
13
  1. Inspect for the leak at the input shaft seal.
  2. Inspect for the following if the input shaft seal is leaking:
    • 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 CSC assembly. Refer to Clutch Concentric Actuator Cylinder Replacement (CTS) .
Did you find and repair the condition?		 Go to Step 25  Go to Step 14 
14
  1. Inspect the case for cracks or porosity.
  2. If cracks and or porosity are found replace the transmission. Refer to Transmission Replacement .
Did you find and repair the condition?		 Go to Step 25  Go to Diagnostic Aids
15 Is the leak at the vehicle speed sensor (VSS)? Go to Step 16  Go to Step 17 
16
  1. Remove the VSS. Refer to Vehicle Speed Sensor Replacement .
  2. Inspect for the following:
    • 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 25  Go to Step 1 
17 Is the leak at the backup light switch? Go to Step 18  Go to Step 19 
18
  1. Remove the backup light switch. Refer to Backup Lamp Switch Replacement .
  2. Inspect for the following:
    • Cross threaded or damaged threads
    • Insufficient sealant
    • Leaking switch
    • Improper installation
Did you find and repair the condition?		 Go to Step 25  Go to Step 1 
19 Is the leak at the shift shaft plunger plug? Go to Step 20  Go to Step 21 
20
  1. Remove the shift shaft detent plug. Refer to Transmission Disassemble  and Transmission Assemble .
  2. Inspect for the following:
    • Loose, not installed properly
    • Insufficient sealant
    • Cracked case
    • Improper installation
Did you find and repair the condition?		 Go to Step 25  Go to Step 1 
21 Is the leak at the sealing flanges of the transmission cases? Go to Step 22  Go to Step 23 
22
  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission. Refer to Transmission Disassemble .
  3. Inspect the sealing surfaces. Refer to Transmission Case Cleaning and Inspection .
Did you find and repair the condition?		 Go to Step 25  Go to Step 23 
23 Is the leak coming from a crack or porosity in the transmission case? Go to Step 24  Go to Diagnostic Aids
24
  1. Remove the transmission. Refer to Transmission Replacement .
  2. Disassemble the transmission. Refer to Transmission Disassemble .
  3. Replace the faulty case. Refer to Transmission Assemble .
Did you find and repair the condition?		 Go to Step 25  Go to Diagnostic Aids
25 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 1 
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