Ok we are dealing with my 2002 GMC 3/4 TonHD, 6.0L 4l80E. the problem is when the engine is cold and a few warm times, the truck seems to have gained some RPM.
40-50 MPH in OD the truck will cycle the rpm up and down like its searching for lockup.
When the rpm went up I down shifted into 3rd. the rpms went up more.. So third is there..
Then upshift the rpm falls ok OD is good.
The the rpm falls and jumps back up then back down.. What the hell..

I thought maybe the turbo tune did some thing, but hell that was just adding a bit of timing and lowering the torque management to 50%. And since I have driving for well over 2 months now and this just started happening, I am clueless.

Took to the dealer for warranty(only had 17days left) and went for a test drive. Mech said seems fine to me... These transmission do not just lock up, the solenoid progressive locksup... Ok that made no since to me..
Any one with any ideas.
at 60mph I am at 2k on the tach, I seem to remember it use to be around 15-1700.

Ricky

 

Yes pulse width modulation converter apply,some shift kits can make it an on/off apply,he got no codes when he drove it? dont tell me he didnt have his tech II with.

 

No I have not checked for codes yet,, we just test drove it, and by feel that is what he said.. I well become a pain if this keeps up.. never annoying.
Ricky

 

Sounds like your converting is randomly locking, unlocking, locking, etc.

 

Well its at the dealer ship again.. Today all day acted up..40mph and setting at 2000rpm then backdown at 1600 this sucks.. So took to the dealers tonight and on the way data logged the drive... Damm thing did not act up 1 time... I did get a wrong gear code from the pcm..
Hopefully tommorrow when its cooled off over night, it will act up.. I am taking the mech. on a test drive, with the efi live connected datalogging just incase it acts up we can review the data...
Only a few days left on the old warranty...

Today the other service writed tried saying it was the turbo's fault... Its not slipping or burned up, its bouncing so luckily hes out and the first guy is in..

Ricky