Special Testing Procedures

Special tests are designed to assist the technician in diagnosing the hydraulic and mechanical portions of the transmission.

Air Pressure Test

A no-drive condition can exist even with correct transmission fluid pressure because of inoperative clutches. Refer to the Clutch Application Chart in this section to determine which clutch is applied in each gear range. A clutch concern can be located through a series of checks by substituting air pressure for fluid pressure to determine the location of the concern.

Example: When the selector lever is in a forward gear range, a no-drive condition may be caused by an inoperative clutch.

1. Drain the transmission fluid. Remove the transmission fluid pan.

2. Remove the transmission fluid filter, seal assembly and the main control unit.

3. Locate the inoperative clutches by applying air pressure into the appropriate clutch port.

4. Apply air pressure to the appropriate clutch port. A dull thud may be heard or movement felt when a clutch piston is applied. If the clutch seals or check ball are leaking, a hissing sound may be heard.

5. If the clutches fail to operate during the air check:
   • the piston seals are not seated, damaged or installed incorrectly.
   • plugged feed holes for clutch apply in the case and/or clutch cylinder.
   • damaged piston and/or clutch cylinder.

6. Service as required and recheck.