I just rebuilt my 4L60E transmission to handle the power of my engine. I have it installed and have 1,2,3 and reverse but I have no overdrive.

I didn't have TCC as well but its because I didn't properly wire it up. I have no DTC's when I use HP tuners.


What could cause me to lose 4th gear only?

 

I have the same problem. I stopped at Advanced to have the codes checked and he said it was one of the throttle position sensors. I checked my ATSG manual and it lists the TPS as a possible cause as well as the fluid pressure switch assy, brake pedal switch and the 2-4 band assy assembled improperly. I'm going to try the TPS first. I realize this is an old post, did you figure out the cause in your case? If so, what was it? Maybe you can help me... Thanks in advance.