Air Pressure Tests

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A "No Drive" condition can exist, even with correct transmission fluid pressure, due to inoperative clutches or bands. Inoperative components can be located through a series of checks by substituting air pressure for fluid pressure to determine location of malfunction. To check component, drain transmission fluid. Remove oil pan, gasket and control valve body. See VALVE BODY under REMOVAL & INSTALLATION in appropriate AUTOMATIC article in TRANSMISSION SERVICING. Install Transmission Test Plate (T95L-77000-AH) and Test Plate Gasket (T95L-77000-AH1).

NOTE: Cover vent in test plate with shop towel to prevent fluid spray. Do not plug or apply air pressure to test plate vent.

Using compressed air at 40 psi (2.8 kg/cm² ) maximum, apply air to appropriate points. See Fig 1. A dull thud can be heard or movement felt when clutch or band is applied. If clutch seals or check balls are leaking, a hissing sound may be heard. If air pressure applied to a clutch passage fails to operate clutch or operates clutches simultaneously, disassemble and check fluid passages in center support and clutches to detect obstructions.

Fig 1: Identifying Air Pressure Test Points

Courtesy of FORD MOTOR CO.