Special Testing Procedures

Special Testing Procedures
The special tests are designed to aid the technician in diagnosing the hydraulic and mechanical portions of the transmission.

Engine Idle Speed Check
Refer to Computers and Control Systems for diagnosis and testing of the engine idle speed.

Air Pressure Test

Air Pressure Test:

A no-drive condition can exist, even with correct transmission fluid pressure, because of inoperative clutches or bands. Refer to the Clutch Application Chart to determine the appropriate elements. 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 (D, 3, 2, 1), a no-drive condition may be caused by an inoperative forward clutch.
1. Drain the transmission fluid. Remove the transmission fluid pan.
2. Remove the transmission fluid filter and seal assembly and the mechatronics unit.
3. The inoperative clutches can be located 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 may be heard.
5. If the clutches fail to operate during the air check:
^ the piston seals are not seated, damaged or not installed correctly.
^ 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.