Special Test Procedures
SPECIAL TESTING PROCEDURESThe special tests are designed to aid the technician in diagnosing the hydraulic and mechanical portions of the transmission.
LINE PRESSURE 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. Do not maintain Wide-Open Throttle (WOT) in any transmission range for more than five seconds or transmission damage may occur.
NOTE: Carry out shift linkage check prior to carrying this test.
This test verifies the line pressure is within specifications.
1. Connect the Transmission Fluid Pressure Gauge to the line pressure tap.
2. Start the engine and check the line pressures. Refer to the Line Pressure Chart to determine if the line pressure is within specification.
3. If the line pressure is not within specifications, carry out On-Board Diagnostics and GO to Pinpoint Test E, air pressure check, and clean, inspect and install a new main control system or pump as required.
Line Pressure Chart
Line Pressure Diagnosis Chart
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:
- Torque converter one-way clutch.
- Forward clutch.
- Low one-way clutch.
- Reverse clutch.
- Overdrive one-way clutch.
- Direct clutch.
- Engine driveability concerns.
Stall Speed Chart
1. Connect a tachometer to the engine.
2. After testing each of the following ranges, O. 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: If the engine rpm recorded by the tachometer exceeds the maximum specified rpm, release the accelerator pedal immediately. Clutch or band slippage is indicated.
CAUTION: Do not maintain Wide-Open Throttle (WOT) in any gear range for more than 5 seconds or damage to the transmission may occur.
Press the accelerator pedal to floor (WOT) in each range. Record the rpm reached in each range. Stall speeds should be in the appropriate range.
If the stall speeds were too high, refer to the following Stall Speed Diagnosis Chart. 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.
Stall Speed Diagnosis Chart
AIR PRESSURE TESTS
Air Pressure Test Port Locations
A no-drive condition can exist, even with correct transmission fluid pressure, because of inoperative clutches or bands. Refer to the Band/Clutch Application Chart 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 manual selector lever is in a forward gear range (0, 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, the solenoid body, the control assemblies and separator plate, upper/lower gaskets.
3. The inoperative clutches can be located by applying air pressure into the appropriate clutch port. See the Air Pressure Test Port Locations illustration for clutch port locations.
4. Apply air pressure to the appropriate clutch port (see diagram). 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, not installed.
- 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.
Torque Converter Drain back Test
1. Drive the vehicle for 30 - 60 minutes to attain normal operating temperature.
2. Check the transmission fluid level. Add fluid only if required.
3. Drive the vehicle through 8 to 10 cycles of 1/2 throttle, 1-2 upshifts to elevate the transmission temperature. Then proceed as follows:
- Park the vehicle on level ground.
- Allow the vehicle to sit for 30 - 60 minutes.
- Check and note the fluid level on the fluid level indicator with the engine off, in PARK.
- The following example shows the fluid level after 45 minutes.
4. Allow the vehicle to sit for a minimum of 24 hours. Check and note the fluid level.
5. If the fluid has risen 25.4 mm (1 inch) or more above the level in the first check, excessive converter drainback has occurred.
6. If excessive drainback has occurred:
- stuck open check ball in rear cooler line case fitting.
- no check ball in rear cooler line case fitting.
- incorrect case cooler line case fitting (without check ball) installed.
7. Service as required and recheck.