Air Pressure Tests

Air Pressure Tests

A NO DRIVE condition can exist, even with correct transaxle 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.
- When the shift control selector lever is in a forward gear range (OD, D, 1), a NO DRIVE condition may be caused by an inoperative forward clutch, overrunning or low/intermediate band.
- No manual low (1) coast could be caused by an inoperative direct clutch, or direct overrunning clutch.
- Failure to drive in reverse (R) could be caused by a malfunction of the reverse clutch, forward clutch or low/intermediate overrunning clutch.

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

Note: Use only dried, regulated (276 kPa (40 psi) maximum) air pressure. Apply air to the appropriate passage. A dull thud should be heard when the clutch or band applies. There should be no hissing sound when clutch or band is fully applied.

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

1. Drain transmission fluid and remove transaxle pan.
2. Remove main control cover.
Then remove pump assembly and main control valve body.
3. Install the Transmission Test Plate T94P-77001-EH, Test Plate Mounting Bolts T82P-7006-C and gasket.
Tighten bolts to 10-12 Nm (7.5-8.8 lb-ft).

Air Pressure Test Plate:

4. Apply air pressure to the appropriate clutch port (refer to diagram). A dull thud may be heard or movement felt when the clutch is applied or released. If clutch seals or check balls are leaking a hissing sound may be heard.

Note: Do not apply air to test plate vent hole.

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

If air pressure applied to the clutch passages fails to operate a clutch, or operates clutches simultaneously, remove and with air pressure, check the fluid passages in the chain cover (7G188), front support, driven sprocket support and clutches to detect obstructions.

If air pressure applied to the accumulator passages fails to operate an accumulator, remove, and with air pressure, check the fluid passages in the chain cover to detect obstructions.