6l90 shifts in, out, then into 6th gear 2010 2500hd

I have a 2010 Chevy 2500hd with a recent reman 6l90 transmission after which the TCM was reprogrammed to the latest GM program. Once the learn process has finished it will shift into 6th, then out and back into 6th. I can do a relearn and it will initially shift fine then progressively go back to the shift in, out, in of 6th. The gear command does not change from 6th when it does this. I think it?s in the TCM tune due to it shifting fine when relearn is in progress. Any ideas would be appreciated.

If you know you have a factory calibration running then something is wrong. Could be torque signal from ECM to TCM, could be VSS signal, could be trans is fucked, could be tune is off, could be ECM TCM mismatch, could be ... could be ... could be ...

As is customary around here a log and tune please...

If its just a factory tune, then you got a bad fluid pump in the transmission. There are alot going around now. the pressure solenoid on the pump is faulty, and the TCC cannot keep converter locked, causing intermittent downshifting. Working on one now for that same reason.

I thought that at first too but why does it not do it in the relearn process? I've also noticed that it also does not do it in tow/haul mode.

Tune and log are now attached. Sorry for the delay. It took a few days to get a good log.

I can see the commanded gear change to 5 as you increased the throttle. The converter unlocks for the shift. Then it locks up a little later. Then it commands back to 6th. That part seems ok. You have a flair at the end of the 5-6 change. Is the ECM and TCM tune stock and correct for the vehicle?

It is supposed to be the most recent tune that GM has released for the vehicle. It was taken to the dealership for the tune after the reman tranny was installed. I was not there for it, the tranny shop took care of that.

How long have you been driving it. If that flare doesn't go away you'll need to take it back to the builder. Yes maybe can tune around it, but that's not the point. Shouldn't have to with a reman and stock tunes.

Reman trans was installed in February. I’ve had it back four times and they just do a relearn and say it is fine. Last time I had it back they said my catalytic converters are probably plugged and the engine is underpowered. Said until I fix that, it wouldn’t shift correctly. They said to drive it, it has a three year warranty. I’m tired of the run around.

Is it a GM reman unit? If so, take it back and tell them to tear it down. Contact GM if needed. I work for a GM dealership and we deal with these everyday. Most of the time, the remans never have an issue. If they are saying your converters are clogged, youd have a P0420 or 430 in it. If that was indeed the case, yes that would cause some issues with shifting, etc. Alot of techs dont want to tear a GM reman down, because its warranty time and you get screwed basically. But, they need to honor their product. If not, depending on where youre located, bring it to my dealership and Ill fix it.

It is not a GM reman. They were four months out when mine went out. I did move the TC lockup speed in 5 and 6 up 2mph and it seems to have helped. I think it was trying to shift and lock up immediately. Maybe the pump doesn’t have enough volume to do both immediately?

Could be just the pump pressure. The rotor vanes in the pump are selectable in size and alot of places will just throw the middle ones in and send it. And sometimes, remans dont even replace pump. Might be able to tune it out.