For 1990-2009 cars

### Diagnostic Aids

Using the incorrect type of transmission fluid may affect the sealing ability of the seals. Ensure the use of the correct type of transmission fluid. The incorrect type of sealer may not be compatible with the transmission 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 Transmission - Aisin AY6.

### Test Description

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

1. 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 manual transmission symptoms 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 in Clutch.

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 in Clutch.

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