Air Pressure Tests

Fig 1: Identifying Transmission Air Test Plate

Courtesy of FORD MOTOR CO.

A no-drive condition can exist even with correct transmission fluid pressure because of inoperative clutches or bands. An erratic shift can be located through a series of checks by substituting air pressure for fluid pressure to determine the location of the malfunction.

Follow the procedure to determine the location of the inoperative clutch or band by introducing air pressure into the various test plate passages.

Apply air to the appropriate passage(s). A dull thud should be felt or heard or movement could be observed when the clutch component applies. There should be no hissing sound when the component is applied.

Cover the vent hole in the test plate with a clean, lint-free shop towel to prevent spray when the air is applied. Plugging the vent hole during testing will result in inaccurate results.

WARNING: If equipped with fire suppression system, refer to FIRE SUPPRESSION SYSTEM for Important Safety Warnings.
1. Drain transmission fluid and remove the transmission fluid pan.
2. Remove the main control valve body.
3. Install transmission test plate and gasket. Tighten bolts to 10 Nm (89 lb-in).
NOTE: Do not apply air to the test plate vent hole.
4. Apply air to the appropriate clutch port (refer to the Fig 1 illustration). A dull thud may be heard or movement felt when the component is applied or released. If clutch seals or check balls are leaking a hissing sound may be heard.

If the servos do not operate, disassemble, clean and inspect them to locate the source of the concern.

If air pressure applied to the clutch passages fails to operate a clutch, or operates clutches simultaneously, inspect the fluid passages in the case.

If air pressure applied to the accumulator fails to operate an accumulator, remove and inspect case passages and piston.