4L80E & TH400 Tech.

[picklito]

Mr. Clinebarger,
Me again. On the same 2003 Yukon/8.1/4L85E that I firmed up previously, I had also been noticing that the shift point RPM seems to be slowly increasing over the last couple years. Even at pretty light throttle around town, every gear seems to hang on just a little too long, and getting longer. Any idea what that might be and how to fix it? There has never been any electronic tuning to the truck. thx.

[clinebarger]

Originally Posted by picklito

Mr. Clinebarger,
Me again. On the same 2003 Yukon/8.1/4L85E that I firmed up previously, I had also been noticing that the shift point RPM seems to be slowly increasing over the last couple years. Even at pretty light throttle around town, every gear seems to hang on just a little too long, and getting longer. Any idea what that might be and how to fix it? There has never been any electronic tuning to the truck. thx.

It is most likely NOT transmission related, It would trip codes if the "Shift Adapts" were maxed out.

Engine performance issues can & will cause the slow progression of later & later shifts, I have fixed similar symptoms with something as simple as a Fuel Filter.
Faulty/Dirty MAF sensor (Torque Rise is calculated by the PCM trough input from the MAF)

[picklito]

Originally Posted by clinebarger

It is most likely NOT transmission related, It would trip codes if the "Shift Adapts" were maxed out.

Engine performance issues can & will cause the slow progression of later & later shifts, I have fixed similar symptoms with something as simple as a Fuel Filter.
Faulty/Dirty MAF sensor (Torque Rise is calculated by the PCM trough input from the MAF)

Great info. Makes perfect sense. Will report back if I find something.