I just put in a junk yard transmission in my 97 grand cherokee with a 5.2 engine. My problem is that it shifts fine, smoothly into Reverse, from 1st to 2nd, when it gets to 3rd it seem's to want to shift after I let off the pedal. It seems to hold tight. I put a little to much fluid in the transmission when I put it in, could that mess with the shifting? I am planning on draining out the extra fluid. Could it be the TPS?