Got a bad deal here. Mike (the guy that I work with) did a trade deal for painting his truck and he had to install a used trans supplied by the truck owner in this 97 Chevy. He got it in and all it had was third and reverse, which almost always means there is an electronic problem. So calls me out to look at it and it has no diagnostic trouble codes whatsoever which is really strange. I pulled the pan off and it's got power to all the solenoids and all the solenoids check good. No fuses blown, no bad grounds, etc. So Mike pulls the trans out and I find a broken sun gear shell in the trans and a few burnt clutches, which would NOT cause this problem of stuck in third. So I fix the trans and he puts it back in and this morning, it's the same! I go drive it and it's starting off in overdrive, then shifts to third, then second and then just starts revving up like the 3-4 clutch is fried but it's not, I replaced it. Besides if it was fried it would not have 3rd or 4th. It's almost like some wires are switched grounding the wrong solenoids to make it work like this. Now I have NEVER seen of these 4l60 transmission behave like this. Ever. The truck is a pile of rust, it has wires hanging down everywhere, no oxygen sensors on what remains of the exhaust system. Mike had another computer and we out it on and no difference. So today we start looking for wiring problems and the bed nearly falls off it because of the rust it has! POS! I find one PCM ground does not have continuity between the computer and where it's grounded to the motor and that now the range sensor has stopped working. So we have decided to stop as this wasn't part of the deal. This truck is basically scrap and the owner of it decided he just wants us to dismantle the whole thing and give him the motor and trans and we'll cut up the rest of it after taking off anything that is usable. The guy didn't want to pay us anymore to track down what ever the hell is wrong with this thing and I was pleased! And so was Mike. He stopped stopped cussing and kicking shit! But seriously I have NEVER seen one do this and I have worked on a countless number of these with varying problems. Can't wait to cut it up!