A/T - Hesitation/Grinding Noise on Low Speed Coastdown
File in Section: 07 - Transmission/TransaxleBulletin No.: 03-07-30-051
Issue Date: October, 2003
Subject:
Low Speed Coast Grinding Noise and/or Hesitation at Vehicle Launch (Install New TCM Calibration)
Models Affected:
2003-2004 VUE Vehicles
2003-2004 ION Vehicles
with VT25E (Vti) Transaxle (RPO M751M16)
Attention: Technician
Condition:
This bulletin addresses two conditions:
Condition # 1:
Some customers may comment on a grinding noise that occurs at approximately 10 mph (16 kph) during a vehicle coast down, in which the driver's foot is off the accelerator.
Condition # 2:
Some customers may comment on the vehicle hesitating during a launch from a stopped position.
Cause:
Cause for Condition # 1: The variable drive belt is commanded to a ratio that causes a unique load on the drive belt, which generates belt noise during a coast down.
Cause for Condition # 2: A condition may exist in which the TCM commands the transaxle to inadvertently select a higher range (more overdrive) than what would be desired for vehicle launching from a stopped position.
Correction:
Install a new TCM calibration based on the following Calibration Information table, and add one unit, 10 cc syringe (.33 fluid oz) of DEX-CVT(R) additive (P/N 22697447). If the calibration and additive do not correct the low speed coast grinding noise condition, perform the Line Pressure Check Procedure located in this bulletin.
The new TCM calibration will not correct a grinding noise condition that occurs at approximately 5 mph (8 kph) during a tip in/tip out throttle maneuver at 1500 RPM. For this condition, perform the Line Pressure Check Procedure located in this bulletin.
Calibration Information
Install one of the TCM calibrations based on the application shown.
Line Pressure Check Procedure
Tools required
J 45195 Line Pressure Gauge
Caution:
Keep the brakes applied at all times in order to prevent unexpected vehicle motion. Personal injury may result it the vehicle moves unexpectedly.
1. Remove the fluid pressure test hole plug from the transaxle.
Important:
Permatex(R) High Temperature Thread Sealant P/N 21485278 (GM P/N 12346004, in Canada P/N 10953480) or equivalent must be applied to the threaded components of the pressure gauge to ensure that no leakage occurs during testing.
2. Ensure that the gear selector is in PARK and the parking brake is set.
3. Install the J45195 line pressure gauge.
4. Install a scan tool.
5. Start the engine and allow the engine to warm up to normal operating temperature.
6. Access the Line PC Solenoid functional test on the scan tool output controls.
Notice:
The total test running time should not be longer than 2 minutes. Running the test longer than 2 minutes may damage the transaxle.
Important:
The scan tool can only control the line pressure control solenoid when the transaxle is in PARK and the engine is running. This protects the transaxle clutches from extremely high or low pressure, as when the transaxle is in DRIVE or REVERSE.
7. With the engine speed at idle, use the scan tool to increase the Line PC Solenoid amperage to 1 amp. Read and record the corresponding line pressure on the pressure gauge.
Important:
In order to obtain the required pressure for the high pressure test point, the engine speed must be 1,400-1,500 RPM. A line pressure reading taken at a lower engine speed will be inaccurate and may lead to misdiagnosis.
8. Slowly increase the engine speed to 1,400-1,500 RPM before performing the next test step.
9. Using the scan tool, decrease the Line PC Solenoid amperage to 0.2 amp. Read and record the corresponding line pressure on the pressure gauge.
10. Shut the engine OFF. Remove the J45195 line pressure gauge.
Important:
Before installing the fluid pressure test hole plug, apply Permatex(R) Medium Grade Threadlocker Blue (P/N 12345382, in Canada P/N 10953489) or equivalent to the threads of the plug.
11. Install the fluid pressure test hole plug.
12. Tighten the plug.
Tighten
Tighten the fluid pressure test hole plug to 9 N.m (7 ft-lbs).
Important:
Pressure readings not within an acceptable range may indicate an internal transaxle leak.
13. If the pressure reading recorded in Step 7 is below 246 psi (1696 kpa), replace the Case Cover Assembly, Valve Body Assembly, and the Oil Cooler Lines. Refer to the appropriate Service Manual for service procedure.
14. If the pressure reading recorded in Step 9 is below 600 psi (4137 kpa), replace the Case Cover Assembly, Valve Body Assembly, and the Oil Cooler Lines. Refer to the appropriate Service Manual for service procedure.
15. If the pressure readings recorded in Step 7 and Step 9 are within acceptable ranges, replace the Case Cover Assembly only. Refer to the appropriate Service Manual for service procedure.
Parts Requirements:
Claim Information:
To receive credit for this repair during the warranty coverage period, submit a claim through the Saturn Dealer System for K5364 (TCM-Reprogramming) and K71 04 (Cover Assembly, Variable Drive and Driven Pulley Assemblies, Belt and Case). Add times have been included under K7104 to perform the "Line Pressure Check Procedure" in this bulletin and to replace the oil cooler lines.
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