Nelson Tune transmission Issue

A few months back I ordered a computer from Nelson for my 2006 Tahoe 4x4.I installed it and everything was fine.I decided I wanted to change to 4.88 gears so I contacted Nelson and had another computer sent with the only change being the gears.I installed it today and followed all procedures with the relearns but now my transmission doesnt seem to be shifting right. I actually hit the rev limit before it shifted out of first gear at about 3/4 throttle.It seems to shift the same as the first tune in all other gears,could it be something I did wrong during the crank relearn? I will try to contact Nelson in the morning but I was just trying to get some opinions before I called them.

Did you think it might be your transmission?

Shift points work off both RPM and speed. So if you just wanted Allen to set the speedometer for the 4.88's, he may not have adjusted the shift points.

just hitting on 1st, all other the same, could be Trans related. Shift Solenoid or tune !

get with Allen,im sure he will help u out..if it keeps doing the same then trans going bye bye

put the other pcm back in and see if it changes

agreed....truck might shift a little hard/ speedo will be off, but if it gets a lot better, there was probably a mix up in one of the tables.


What size tires are you running with a gear that big? Make sure you measure from the ground to the top of the tire when installed on vehicle, and send him that measurement for the diameter. A "36" can measure anywhere between 34 and 37 inches depending on brand. When getting in gears that big, any difference can make a big difference in the calculations for shift points. When I went from 3.73 to 4.56 my speedo was WAY off on the ride home until I threw in the new tune.