My tranny was rebuilt about 2years or so ago. (2006 GMC Crew cab with the 4.8/60E)... Its been doing it, I guess afew months after the rebuild.. While normal driving and it goes into OD,if I start to incline up a hill or kinda lose speed it will want to shimmy and not jump down a gear for alittle bit..I can either let off the gas or give it more and let it jump down and pick up some speed..Then it will be fine, Anyone have a cuase for this? The bands alittle off inside..I have EFI Live on the truck and we did bump the shift points up alittle and it did help some.. Also everynow and then,and it's not all the time I will be at a stop light and let off the brake and the truck will creep afoot or 2..If I hit the brake again,then left off and push the gas it seems as if theres a soft bump and it goes into gear...I dont think its the brakes sticking.. Any idea's?
thanks

 

What RPM when you're climbing an incline?
Almost sounds like the engine is lugging with the converter locked.
Can you data log with EFILive?
Sounds like the trans may only downshift to second sometimes and then shifts to first when you hit the gas maybe.

 

ya we could data log..We always use my buddy's laptop and he works offshore for 2-weeks,then home... I would say im usually around 45ish MPH and I think thats usually in 3rd? which would be around 1400 according to the dash...Sometimes I even take it out of drive and into 3rd to help the truck move along..Then I'll upshift it when i get more into the rpms.. I could pay more attention tomorrow and give more details to that though.. Until I can data log.

 

Alright watched it today, I will be around the 45mph range and rpms would be around 1100...

 

Sounds like the converter locks and lugs the engine. When your buddy gets back in town take a look at when the TC locks and maybe bump it up to 50 mph. Also look at the throttle % before the converter unlocks and maybe bumpy that % down some.
An easy way to tell if it's the converter locking in the meantime is to press the Tow/Haul button right after 45 mph and the rpm's drop down to 1100 and see if the shimmie goes away as the converter unlocks.

 

I do know, if I have it in tow/haul mode I wont have any shimm'ing since it holds the RPMS up alittle more before it switch's gears..I Have also dropped it into 3rd gear to make it gain more RPMS when it shimm'ies and it climbs fine... Maybe I just need to bump 3rd and OD up on EFI live? I think we did do that,maybe not..
Thanks for the help, I'll get in touch with my buddy though..

 

Sounds like a good plan. Delay the converter lockup in OD or lock the converter in 3rd and delay 4th some.