Stall Speed Test

The Stall Speed Test checks:

• torque converter clutch operation and installation.
• forward clutch.
• low one-way clutch.
• reverse clutch.
• low intermediate band.
• driveability concerns.

Carry out this test with the engine coolant and transmission fluid at correct levels and at normal operating temperature.

Apply the parking brake firmly for each Stall Speed Test.

1. Find the specified stall rpm for the vehicle. Refer to the Stall Speed Chart. Use a grease pencil to mark the rpm on the dial of a tachometer.
   Fig 1: Identifying Stall Speed Chart

   Courtesy of FORD MOTOR CO.
2. Connect a tachometer to the engine.
NOTE: If the rpm recorded by the tachometer exceeds the maximum limits, release the accelerator pedal immediately because clutch or band slippage is indicated.
3. In each of the following ranges (D), D, 1, R, press the accelerator pedal to the floor and hold it just long enough to let the engine get to wide open throttle (WOT). While making this test, do not hold the throttle open for more than 5 seconds at a time.
4. Note the results in each range.
5. After each range, move the selector lever to NEUTRAL and run the engine at 1,000 rpm for about 15 seconds to cool the torque converter before making the next test.
6. Refer to the following chart for corrective actions.
NOTE: The stall speed in REVERSE will be lower.
7. If stall speeds were too high, refer to the following chart. If stall speeds were too low, first check engine idle speed and tuneup. If engine is OK, remove torque converter and check torque converter clutch for slippage.

Fig 2: Identifying Stall Speed Diagnosis Chart

Courtesy of FORD MOTOR CO.

Fig 3: Identifying Transaxle 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 failure.

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 component applies. There should be no hissing sound when the 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 the air is applied. Plugging the vent hole during testing will result in inaccurate results.

1. Drain transmission fluid and remove the transaxle fluid pan. For additional information, refer to TRANSMISSION FLUID DRAIN AND REFILL .
2. Remove the main control valve body.
3. Install Transmission Test Plate and Gasket. Tighten bolts to 11Nm (8 lb-ft).
NOTE: Do not apply air to the test plate vent hole.
4. Apply air to the appropriate clutch port (refer to the diagram). 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.