Stall Speed Test

This test checks operation of the following items:

• Torque converter clutch
• Forward clutch
• Low one-way clutch (OWC) assembly
• Driveability concerns

1. Connect tachometer to the engine.
CAUTION: After testing each of the following ranges (D), 2,1, and R, move the transmission range selector lever to N (NEUTRAL) and run engine at 1,000 RPM for about 15 seconds to allow the torque converter to cool before testing the next range.
CAUTION: Do not maintain wide open throttle in any range for more than five (5) seconds.
CAUTION: If the engine RPM recorded by the tachometer exceeds maximum specified RPM, release the accelerator pedal immediately. Clutch or band slippage is indicated.
NOTE: Prolonged use of this procedure may set Diagnostic Trouble Code P0712, P1783. After carrying out Stall Speed Test run OBD Test and clear DTCs from memory.
Fig 1: Air Pressure Tests
Courtesy of FORD MOTOR CO.
NOTE: Use only dry, regulated 276 kPa 40 psi maximum air pressure.
NOTE: 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.
2. Press accelerator pedal to floor (WOT) in each range. Record RPM reached in each range. Stall speeds should be as follows:
   STALL SPEED CHART
   
   

   Vehicle	Engine	RPM
   Explorer Sport Trac	4.0L	2,495-2,938

   If stall speeds were too high, see the Stall Speed Diagnosis Chart. If stall speeds were too low, first check the engine idle speed. If engine idle is OK, remove torque converter and check the torque converter clutch for slippage.

   STALL SPEED DIAGNOSIS CHART
   
   

   Transmission Range Selector Lever Position	Stall Speeds High	Stall Speeds Low
   (D)Overdrive, D, and 1	Front One-Way Clutch, Rear One-Way Clutch	-
   D,2 and 1	Forward Clutch, Front One-Way Clutch	-
   (D)Overdrive	Forward Clutch, Front One-Way Clutch	-
   (D)Overdrive, D, 2, 1 and R	General Pressure Concerns, Forward Clutch, Front One-Way Clutch	Converter One-Way Clutch or Driveability Concerns
   R Only	Reverse Band, Direct Clutch, Low/Reverse Servo	-
   2 Only	Intermediate Band/Servo	-
   1 Only	Low/Reverse Band/Servo	-

   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 component applies. There should be no hissing sound when the component is fully applied.

3. Drain transmission fluid and remove the transmission fluid pan.
4. Remove the main control valve body.
5. Install transmission test plate and gasket. Tighten bolts to 11 Nm (8 lb-ft).
6. 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.
7. Install the main control valve body after testing is complete and any repairs have been made.

If test results find that 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 another clutch simultaneously, disassemble and use air pressure to check the fluid passages in the center support and clutches to detect obstructions.