Road Test Procedure
4L80-E / 4L85-E AUTOMATIC TRANSMISSIONRoad Test Procedure
The following test provides a method of evaluating the condition of the automatic transmission. The test is structured so that most driving conditions would be achieved. The test is divided into the following parts:
^ Electrical Function Check
^ Upshift Control and Torque Converter Clutch (TCC) Apply
^ Part Throttle Detent Downshifts
^ Full Throttle Detent Downshifts
^ Manual Downshifts
^ Coasting Downshifts
^ Manual Gear Range Selection
- REVERSE
- Manual FIRST
- Manual SECOND
- Manual THIRD
Important: Complete the test in the sequence given. Incomplete testing cannot guarantee an accurate evaluation.
Before the road test, ensure the following:
^ The engine is performing properly.
^ Transmission fluid level is correct.
^ Tire pressure is correct.
During the road test:
^ Perform the test only when traffic conditions permit.
^ Operate the vehicle in a controlled, safe manner.
^ Observe all traffic regulations.
^ View the scan tool data while conducting this test.Take along qualified help in order to operate the vehicle safely.
^ Observe any unusual sounds or smells.
After the road test, check the following:
^ Transmission fluid level.
^ Diagnostic Trouble Codes (DTCs) that may have set during the testing. Refer to the applicable DTC.
^ Scan tool data for any abnormal readings or data.
Electrical Function Check
Perform this check first, in order to ensure the electronic transmission components are connected and functioning properly. If these components are not checked, a simple electrical condition could be misdiagnosed.
1. Connect the scan tool.
2. Ensure the gear selector is in PARK and set the parking brake.
3. Start the engine.
4. Verify that the following scan tool data can be obtained and is functioning properly. Refer to Scan Tool Data List for typical data values. Testing and Inspection Data that is questionable may indicate a concern.
^ Engine speed
^ Transmission input speed, turbine
^ Transmission output speed
^ Vehicle speed
^ TFP manual valve position switch
^ Transmission range, engine list
^ 4WD low
^ Commanded gear
^ PC solenoid reference current
^ PC solenoid actual current
^ PC solenoid duty cycle
^ Brake switch
^ Engine coolant temperature
^ Transmission fluid temperature
^ Throttle angle
^ Ignition voltage
^ 1-2 shift solenoid
^ 2-3 shift solenoid
^ TCC solenoid duty cycle
^ TCC slip speed
5. Monitor the brake switch signal while depressing and releasing the brake pedal. The scan tool should display:
^ Closed when the brake pedal is released
^ Open when the brake pedal is depressed
6. Check the garage shifts
1. Apply the brake pedal and ensure the parking brake is set.
2. Move the gear selector through the following ranges:
1. PARK to REVERSE
2. REVERSE to NEUTRAL
3. NEUTRAL to DRIVE
3. Pause 2-3 seconds in each gear position.
4. Verify the gear engagements are immediate and not harsh.
7. Important: Harsh engagement may be caused by any of the following conditions:
^ High idle speed-Compare engine idle speed to desired idle speed.
^ Commanded low PC solenoid current-Compare PC solenoid reference current to PC solenoid actual current.
^ A default condition caused by certain DTCs that result in maximum line pressure to prevent slippage
Important: Soft or delayed engagement may be caused by any of the following conditions:
^ Low idle speed Compare engine idle speed to desired idle speed.
^ Low fluid level
^ Commanded high PC solenoid current Compare PC solenoid reference current to PC solenoid actual current.
^ Cold transmission fluid Check for low transmission fluid temperature.
Monitor transmission range on the scan tool, engine list.
7. Apply the brake pedal and ensure the parking brake is set.
8. Move the gear selector through all ranges.
9. Pause 2-3 seconds in each range.
10. Return gear selector to PARK.
11. Verify that all selector positions match the scan tool display.
8. Check throttle angle input.
0. Apply the brake pedal and ensure the parking brake is set.
1. Ensure the gear selector is in PARK.
2. Monitor throttle angle while increasing and decreasing engine speed with the throttle pedal. The scan tool throttle angle should increase and decrease with engine speed.
If any of the above checks do not perform properly, record the result for reference after completion of the road test.
Upshift Control and Torque Converter Clutch (TCC) Apply
The PCM calculates the upshift points based primarily on two inputs: throttle angle and vehicle speed. When the PCM determines that conditions are met for a shift to occur, the PCM commands the shift by closing or opening the ground circuit for the appropriate solenoid.
Perform the following steps:
1. Refer to Shift Speed and choose a throttle position of 10 percent, 25 percent or 50 percent. All throttle angles shown should be tested to cover the normal driving range.
2. Monitor the following scan tool parameters:
^ Throttle angle
^ Vehicle speed
^ Engine speed
^ Output shaft speed
^ Commanded gear
^ Slip speed
^ Solenoid states
3. Place the gear selector in the OVERDRIVE position.
4. Accelerate the vehicle using the chosen throttle angle. Hold the throttle steady.
5. As the transmission upshifts, note the vehicle speed when the shift occurs for each gear change. There should be a noticeable shift feel or engine speed change within 1-2 seconds of the commanded gear change.
6. Compare the shift speeds to the Shift Speed table. Refer to Shift Speed. Shift Speed Shift speeds may vary slightly due to transmission fluid temperature or hydraulic delays in responding to electronic controls.
^ Note any harsh, soft or delayed shifts or slipping.
^ Note any noise or vibration.
7. Repeat steps 1-6 to complete all throttle angles.
8. Important: The TCC will not engage until the engine is in closed loop operation. The vehicle must be in a near-cruise condition, not accelerating or coasting, and on a level road surface.
Check for TCC apply in THIRD and FOURTH gear. Typical apply speeds in FOURTH gear range from 72-88 km/h (45-55 mph) depending on engine size, engine type and axle ratio.
^ Note the TCC apply point. When the TCC applies there should be a noticeable drop in engine speed and a drop in slip speed to below 100 RPM. If the TCC apply can not be detected:
^ Check for DTCs.
^ Lightly tap and release the brake pedal. The TCC will release.
Part Throttle Detent Downshift
1. Place the gear selector in the OVERDRIVE position.
2. Accelerate the vehicle to 64-88 km/h (40-55 mph) in FOURTH gear.
3. Quickly increase throttle angle to greater than 50 percent.
4. Verify the following:
^ The TCC releases
^ The transmission downshifts immediately to THIRD gear
Full Throttle Detent Downshift
1. Place the gear selector in the OVERDRIVE position.
2. Accelerate the vehicle to speeds of 64-88 km/h (40-55 mph) in FOURTH gear.
3. Quickly increase throttle angle to 100 percent (WOT).
4. Verify the following:
^ The TCC releases
^ The transmission downshifts immediately to SECOND gear
Manual Downshifts
The shift solenoid valves do not control manual downshifts. All manual downshifts are hydraulic. The solenoid states will change during, or shortly after, a manual downshift is selected.
Manual 4-3 Downshift
1. Place the gear selector in the OVERDRIVE position.
2. Accelerate the vehicle to 64-88 km/h (40-55 mph) in FOURTH gear.
3. Release the throttle while moving the gear selector to THIRD.
4. Verify the following:
^ The transmission downshifts immediately to THIRD gear
^ The engine slows the vehicle
Manual 4-2 Downshift
1. Place the gear selector in the OVERDRIVE position.
2. Accelerate the vehicle to 64-72 km/h (40-45 mph).
3. Release the throttle while moving the gear selector to SECOND.
4. Verify the following:
^ The TCC releases
^ The transmission downshifts immediately to SECOND gear
^ The engine slows the vehicle
Manual 4-1 Downshift
1. Place the gear selector in the OVERDRIVE position.
2. Accelerate the vehicle to 64 km/h (40 mph).
3. Release the throttle while moving the gear selector to FIRST.
4. Verify the following:
^ The TCC releases
^ The transmission immediately downshifts to FIRST Gear.
^ The engine slows the vehicle.
Coasting Downshifts
1. Place the gear selector in the OVERDRIVE position.
2. Accelerate the vehicle to FOURTH gear with the TCC applied.
3. Release the throttle and lightly apply the brakes.
4. Verify the following:
^ The TCC releases
^ Downshifts occur at speeds shown in the Shift Speed table. Refer to Shift Speed. Shift Speed
Manual Gear Range Selection
The shift solenoids control the upshifts in the manual gear ranges.
Perform the following tests using 10 percent to 15 percent throttle angle.
Reverse
1. With the vehicle stopped, move the gear selector to REVERSE.
2. Slowly accelerate the vehicle.
3. Verify that there is no noticeable slip, noise or vibration.
Manual First
1. With the vehicle stopped, move the gear selector to FIRST.
2. Accelerate the vehicle to 32 km/h (20 mph).
3. Verify the following:
^ No upshifts occur.
^ The TCC does not apply.
^ There is no noticeable slip, noise, or vibration.
Manual Second
1. With the vehicle stopped, move the gear selector to SECOND.
2. Accelerate the vehicle to 57 km/h (35 mph).
3. Verify the following:
^ The 1-2 shift occurs.
^ The 2-3 shift does not occur.
^ There is no noticeable slip, noise, or vibration.
Manual Third
1. With the vehicle stopped, move the gear selector to THIRD.
2. Accelerate the vehicle to 64 km/h (40 mph).
3. Verify the following:
^ The 1-2 shift occurs.
^ The 2-3 shift occurs.
^ There is no noticeable slip, noise, or vibration.