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Stall Speed Test

WARNING: Apply the service and parking brakes firmly while carrying out each stall test.
CAUTION: Carry out the Line Pressure Test prior to carrying out the Stall Speed Test. If line pressure is low at stall, do not carry out the Stall Speed Test or further transmission damage will occur.
NOTE: The stall test should only be carried out with the engine and transmission at normal operating temperatures.

The stall test checks the operation of the following items:

  1. Connect a tachometer to the engine.
  2. After testing each of the following ranges, D6/D4, 2, 1 and R, move the transmission range selector lever to N (NEUTRAL) and run the engine for about 15 seconds to allow the torque converter to cool before testing the next range.
    3. CAUTION:
    1. If the engine rpm recorded by the tachometer exceeds the maximum specified rpm, release the accelerator pedal immediately. Clutch slippage is indicated.
    2. Do not maintain wide-open throttle (WOT) in any gear range for more than 5 seconds or damage to the transmission may occur.
  3. Press the accelerator pedal to the floor (WOT) in each range. Record the rpm reached in each range. Stall speeds should be in the appropriate range.
STALL SPEED TABLE

Series Engine Min. Max.
Navigator 5.4L 3V 1,650 2,150

If the stall speeds were too high, refer to the following STALL SPEED DIAGNOSIS TABLE . If the stall speeds were too low, check engine tune-up. If the engine is OK, remove the torque converter and check the torque converter reactor one-way clutch for slippage.

Air Pressure Test 

Fig 1: Identifying Air Pressure Test Ports
G04627684Courtesy of FORD MOTOR CO.

A no-drive condition can exist, even with correct transmission fluid pressure, because of inoperative clutches or bands. Refer to the CLUTCH APPLICATION TABLE  to determine the appropriate elements. A clutch concern can be located through a series of checks by substituting air pressure for fluid pressure to determine the location of the concern.

Example: When the transmission range selector lever is in a forward gear range (D6/D4, 2, 1), a no-drive condition may be caused by an inoperative forward clutch.

  1. Drain the transmission fluid. Remove the transmission fluid pan.
  2. Remove the filter and seal assembly and the mechatronics unit.
  3. The inoperative clutches can be located by applying air pressure into the appropriate clutch port.
  4. Apply air pressure to the appropriate clutch port. A dull thud may be heard or movement felt when a clutch piston is applied. If the clutch seals or check ball are leaking, a hissing may be heard.
  5. If the clutches fail to operate during the air check:
    • the piston seals are not seated, damaged or not installed correctly.
    • plugged feed holes for clutch apply in the case and/or clutch cylinder.
    • damaged piston and/or clutch cylinder.
  6. Service as required and recheck.
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