Road Testing Vehicle
Note: Always drive the vehicle in a safe manner according to the driving conditions and obey all traffic laws.The shift point road test and torque converter operation tests provide diagnostic information on transmission shift controls and torque converter operation.
SHIFT POINT ROAD TEST
4R70W Shift Speeds Axle Ratio 2.73:1
4R70W Shift Speeds Axle Ratio 3.08:1
4R70W Shift Speeds Axle Ratio 3.55:1 (Police Package)
This test verifies that the shift control system is operating correctly.
1. Bring engine and transmission up to normal operating temperature.
2. Operate vehicle with transmission range selector lever in D position.
3. Note: Shift speed ranges are approximate for all applications.
Apply minimum throttle and observe speeds at which upshift occurs and torque converter engages.
4. With the transmission in Overdrive (fourth gear), press the transmission control switch. The transmission should downshift to third gear. Release the accelerator pedal; engine braking should occur.
5. Press accelerator pedal to floor, Wide Open Throttle (WOT). Transmission should shift from third to second gear, or third to first, depending on vehicle speed. Torque converter clutch should disengage and then reapply.
6. With the transmission in (D) position and speed above 80 km/h (50 mph) and less than half throttle, move the transmission range selector lever from (D) position to manual 2 position and remove pressure from the accelerator pedal. Transmission should immediately downshift into second gear. With vehicle remaining in manual 2 position, move the transmission range selector lever into manual 1 position, and release accelerator pedal. Transmission should downshift into first gear at speeds approximately below 45 - 56 km/h (28 - 35 mph).
7. If transmission fails to upshift/downshift or torque converter clutch does not apply and release, refer to Diagnosis by Symptom. 4R70W
TORQUE CONVERTER DIAGNOSIS
Prior to torque converter installation, all diagnostic procedures must be followed. This is to prevent the unnecessary installation of new or remanufactured torque converters. Only after a complete diagnostic evaluation can the decision be made to install a new torque converter.
Begin with the normal diagnostic procedures as follows:
1. Preliminary Inspection.
2. Know and understand the customer's concern.
3. Verify the condition-carry out the torque converter operation test.
4. Carry out diagnostic procedures.
- Carry out on-board diagnostics.
+ Repair all non-transmission related DTCs first.
+ Repair all transmission DTCs.
+ Rerun on-board diagnostic to verify repair.
- Carry out Line Pressure Test.
- Carry out Stall Speed Test.
- Carry out Diagnostic Routines.
+ Use the Diagnosis by Symptom Index to locate the appropriate routine that best describes the symptom(s). The routine will list all possible components that may cause or contribute to the symptom. Check each component listed; diagnose and repair as required before changing the torque converter.
Torque Converter Operation Test
Torque Converter Road Evaluation Form
This test verifies that the torque converter clutch control system and the torque converter are operating correctly.
1. Carry out Quick Test with scan tool. Check for DTCs.
2. Connect a tachometer to the engine.
3. Bring the engine to normal operating temperature by driving the vehicle at highway speeds for approximately 15 minutes in OD position.
4. After normal operating temperature is reached, maintain a constant vehicle speed of about 80 km/h (50 mph) and tap brake pedal with the left foot.
5. Engine rpm should increase when brake pedal is tapped, and decrease about five seconds after pedal is released. If this does not occur, see torque converter operation concerns.
6. If the vehicle stalls in (D) or manual 2 at idle with vehicle at a stop, move the transmission range selector lever to manual 1 position. If the vehicle stalls, see torque converter operation concerns. If the vehicle does not stall in (D), refer to Diagnosis by Symptom.
7. If the vehicle exhibits a vibration during the road test complete the Road Test Evaluation Form. This form will aid the technician in determining the source of the vibration.
Note: The following is a list of common vehicle concerns that have been misdiagnosed as torque converter clutch shudder.
- Spark plugs-check for cracks, high resistance or broken insulators.
- Plug wires.
- Fuel injector-filter may be plugged.
- Fuel contamination-engine runs poor.
- EGR valve-valve may let in too much exhaust gas and cause engine to run lean.
- Vacuum leak-engine will not get correct air/fuel mixture.
- MAP/MAF sensor-improper air/fuel mixture.
- HO2S sensor-too rich/lean air/fuel mixture.
- Fuel pressure-may be too low.
- Engine mounts-loose/damaged mounts can cause vibration concerns.
- Axle joints-check for vibration.