1995 4L80E vs 1998 4L80E ~ Using a '427 PMC $OE/$31

[RobertISaar]

TIS should be used for more than TCC slip...



engine RPM - TIS RPM = Torque converter slip RPM
TIS RPM X known commanded gear ratio = expected TOS RPM
read TOS RPM - expected TOS RPM = clutch slip

[1project2many]

TIS should be used for more than TCC slip...

Yes... it helps generate dreaded "undefined gear ratio" or "transmission component slipping" codes.

TCC control strategy and the actual clutch material should be matched up. Pre 95 transmissions used an "on/off" apply strategy while later units added a PWM solenoid to gradually increase pressure and smooth TCC application.

But, the 4L80E always used a PWM TCC solenoid and only had 1 TCC solenoid.

Yes, only one solenoid. But not always PWM for apply / release control. From GM Powertrain 4L80E manual 17001.17-1 "Also some models do not use the duty cycle to control release and simply de-energize the PWM solenoid to release the converter clutch."

The way I remember it, the TCC solenoid had a different part number and higher resistance in the early years. Or maybe it was just diesels with the TCM.

--> I only remember this because I once spent a fair amount of time in trying to diagnose why the new R3500 4L80E trucks in our fleet arrived not doing what GM's own literature said they were supposed to do. Turned out the General had an escape clause. "Those models don't work that way." Thanks, guys. They also had to be sent back to have the dual stator converters removed. Maybe they made lotsa torque, but they accelerated like tired dogs.

[dave w]

I need to update this tread; the vehicle owner has decided to go with a Vortec L31 engine using the 1998 PCM or maybe the LS '0411 PCM from a 2001 ~ 2002 Express Van. The TBI engine is not going to be used.

dave w