Special Testing Procedures

Special Testing Procedures





The special tests are designed to aid the technician in diagnosing the hydraulic and mechanical portions of the transmission.

Line Pressure Test

Line Pressure Tap Plug





NOTICE: Carry out the Line Pressure Test prior to carrying out the Stall Speed Test. If the line pressure is low at stall, do not carry out the Stall Speed Test or further transmission damage will occur. Do not maintain Wide Open Throttle (WOT) in any transmission range for more than 5 seconds.

This test verifies that the line pressure is within specification.

1. NOTICE: The line pressure tap is an M10 X 1.00 thread. Do not use a National Pipe Thread (NPT) fitting when installing a pressure gauge. If a NPT (National Pipe Thread) fitting is used, damage to the transmission case will occur.

Connect the Transmission Fluid Pressure Gauge to the line pressure tap using an M10 X 1.00 fitting.

2. Start the engine and check the line pressures. Refer to the Line Pressure Chart to determine if the line pressure is within specification.

Line Pressure Chart - Diesel Engines

NOTE: Actual and commanded pressures vary based on calibration and transmission adaptive strategies. All pressures listed are approximate.





a Commanded pressure as viewed on diagnostic equipment.

Line Pressure Chart - Gas Engines

NOTE: Actual and commanded pressures vary based on calibration and transmission adaptive strategies. All pressures listed are approximate.





a Commanded pressure as viewed on diagnostic equipment.

3. If the line pressure is not within specification, refer to the Line Pressure Diagnosis Chart.

4. When the pressure tests are complete, install the line pressure tap plug.
- Tighten to 11 Nm (97 lb-in).


Line Pressure Diagnosis Chart






Stall Speed Test

NOTICE: Carry out the Line Pressure Test prior to the Stall Speed Test. If line pressure is low, do not carry out the stall test or additional transmission damage will occur. Do not maintain Wide Open Throttle (WOT) in any gear range for more than 5 seconds.

NOTE: After testing each of the ranges, move the selector lever into the NEUTRAL position and run the engine at 1,000 rpm for about 15 seconds to allow the torque converter to cool off before continuing onto the next range.

NOTE: If the engine speed exceeds maximum specified rpm, release the accelerator pedal immediately.

NOTE: Only perform the stall speed test with the engine and transmission at normal operating temperatures.

The Stall Speed Test checks the operation of the following items:

- Torque converter reactor One-Way Clutch (OWC)

- Forward clutch

- Low OWC (One-Way Clutch)

- Overdrive OWC (One-Way Clutch)

- Engine driveability concerns

1. Connect a scan tool.

2. Press the accelerator pedal to WOT (Wide Open Throttle) in each range. Record the rpm reached in each range. Stall speeds should be in the appropriate range.

Stall Speed






Stall Speed Diagnosis Chart






Air Pressure Test










A no-drive condition can exist even with correct transmission fluid pressure because of inoperative clutches. Refer to the Clutch Application Chart to determine which clutch is applied in each gear range. 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 selector lever is in a forward gear range, 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 transmission fluid filter and seal assembly along with the main control.

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 sound may be heard.

5. If the clutches fail to operate during the air check:
- the piston seals are not seated, damaged or installed incorrectly.

- plugged feed holes for clutch apply in the case and/or clutch cylinder.

- damaged piston and/or clutch cylinder.

- damaged or missing shaft seals in clutch circuit.

6. Service as required and recheck.