Air Pressure Tests

Fig 1: Identifying Air Pressure Tests Locations (Plate Layout Diagram)

Courtesy of FORD MOTOR CO.

A no-drive or erratic shift condition may be due to inoperative bands and clutches. To diagnose these conditions a series of checks can be made by substituting air pressure for fluid to determine the location of the damaged or obstructed component.

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

1. Remove the main control valve body. Refer to MAIN CONTROL VALVE BODY .
2. Install the Transmission Test Plate and gasket. Tighten screws to 10 Nm (89 lb-in).
NOTE: Do not apply air to the test plate vent hole.
3. Apply air to the appropriate clutch or servo port (refer to Fig 1 ). Refer to the AIR PRESSURE TEST DIAGNOSTIC CHART  for conditions, possible causes and actions.
4. After the testing is completed, remove the Air Test Plate and Gasket and proceed with any repairs that are needed.
5. After the repairs are completed, install the Main Control Valve Body. Refer to MAIN CONTROL VALVE BODY .
   AIR PRESSURE TEST DIAGNOSTIC CHART
   
   

   Condition	Possible Causes	Actions
   Dull thud heard or movement felt when air is applied and released	Clutches, bands and fluid passages are OK	Concerns may not be in the transmission. Check the Powertrain Control Module (PCM), wiring harness and non transmission related components.
   No Drive	Clutches and bands inoperative	Disassemble the transmission, clean and inspect to locate area of concern.
   Erratic Shifts	Clutches and bands inoperative due to incorrect pressures	Disassemble the transmission, clean and inspect to locate area of concern.
   No dull thud heard	Clutches, bands and fluid passages may be damaged or obstructed	Disassemble the transmission, clean and inspect to locate area of concern.
   No movement felt	Clutches, bands and fluid passages may be damaged or obstructed	Disassemble the transmission, clean and inspect to locate area of concern.
   Hissing sound heard	Clutch seals or check ball may be damaged or leaking	Disassemble the transmission, clean and inspect to locate area of concern.
   Servos do not operate	Seals and pistons may be damaged. Supply and release ports may be obstructed. Spring may be broken	Disassemble the transmission, clean and inspect to locate area of concern.
   Multiple clutches are applied	Fluid passages in the center support or the clutch cylinders may be obstructed.	Disassemble the transmission, clean and inspect to locate area of concern. Check fluid passages in the center support for obstructions.