I have put a 2001 6.0/4l80E in my 1993 Yukon. It is pretty much stock other than a cold air intake. My problem is while driving down the road and the trans is in 4th and in lock when I floor it the trnas shifts back to 3rd then in to 2nd. I am pretty sure I used a stock program, I just changed for my gears and tires and moved the shift points up a little. is it in my tune or do I have a internal trans problem?I have attached my latest .tun
Thanks in advance.