A/T - 45RFE Does Not Shift Smoothly: Overview

NUMBER: 21-13-99

GROUP: Transmission

DATE: Sep. 3, 1999

SUBJECT:
45RFE Drive Learn Procedure

OVERVIEW:
This bulletin involves a drive procedure of the 45RFE transmission that the technician may use to have the Transmission Control Module (TCM) learn the optimal shift parameters.

MODELS:
2000 (AN) Dakota
2000 (DN) Durango
1999-2000 (WJ) Grand Cherokee

SYMPTOM/CONDITION:

The transmission may not shift smoothly. This condition may occur even after a Quick Learn procedure has been completed.

DIAGNOSIS:

The 45RFE transmission adapts to its mechanical tolerances by learning the clutch volume indexes (CVI's) as well as the duty cycle and other parameters that control shift quality. Performing a Quick Learn will simply reset all transmission adaptive values to factory preset values and it will exercise the transmission clutches to learn an approximate value for the clutch CVI's.

Quick Learn should not be used as a remedy for shift quality complaints. Quick Learn resets more than 70 learn parameters to their preset values and will require them to be relearned.

Quick Learn should only be used when a transmission has be replaced or overhauled, or when the Transmission Control Module has been replaced or flashed. Once Quick Learn is performed, an initial drive evaluation should be performed to determine if the transmission is shifting smoothly.

NOTE:
VERIFY THAT ALL APPLICABLE TECHNICAL SERVICE BULLETINS FOR SHIFT QUALITY HAVE BEEN PERFORMED PRIOR TO PERFORMING THE DRIVE LEARN PROCEDURE.

EQUIPMENT REQUIRED:

1 CH6000 Scan Tool (DRB III(R))
1 CH7000/7001 J1962 Cable

The first step is to verify that the shifter linkage is adjusted properly and that the CHECK PRNDL fault (code 28) is not present.

NOTE:
A MISADJUSTED SHIFTER WILL NOT SET CODE 28. A MISADJUSTED SHIFTER CABLE WILL HOWEVER CAUSE POOR 2-3 SHIFT QUALITY.

It is critical that the PRNDL code be OD when the shifter is in the OD position gate. Use the DRB III(R) to confirm that the correct code is present. If the shifter has a temporary code (T3 or T4) in the OD shifter position, then this is the most likely cause for consistent poor 2-3 shift quality. If the linkage is out of adjustment, then adjust the shifter linkage.

Perform the portion of the 45RFE Drive Learn Procedure that will learn the specific shift characteristic for the shift problem in question.

POLICY: Information Only