Hi all, I sure hope there's someone out there that can help me with this one.
Car is a 2010 Challenger SE that we had the V6 pulled out and a 5.7 put in it with the 6.1 heads and cam, Nag1 transmission was completely rebuilt by Dodge dealership 2 years ago.
I just got done swapping out the 3.91 Getrag 226mm diff for a 3.06 Getrag 226mm. Swap went fine no hiccups at all and it took my time. As soon as complete I used HP tuners reset the gear ratio to 3.06 and did a throttle relearn. When I fired it up I got the red lightning bolt of death. Over the next day or so I did two resets of the throttle relearn through HP tuners to manuals but nothing was taking. Order a new throttle body and was waiting on parts when I went to move the car because when you put it in gear there was no accelerator pedal and on a whim I did it with one last throttle reload manually and that one seem to take. Red lightning bolt was gone car seem to be running fine. Did a quick drive down the road not really going any type of speed over 35 or so came back and then did a quick ride height adjustment. Got on the road today went on the freeway and quickly realized the car is not shifting out past third gear. Runs great right up to that with throttle and everything but holds that gear on it will not shift out. All of my shift points are really close to stock since having this problem for testing. I then started to notice that going from drive to reverse it takes forever for reverse to kick in if it does it all. Car seems a little sluggish off the line but that just might be my throttle curves. I don't have any dtcs or warning lights transmission sounds good differential feels good I just have no idea. I went so far as to pulling an old TCM that I had as a spare putting that one back in and reprogramming it with a tune beard from a stock Challenger with all stock transmission settings etc still no change.

Any help is going to be great because this car has really just been a challenge. Pardon the pun, but I'm at the end of my rope and about ready to watch it go up in a bonfire to be honest with you.

Thanks in advance