OK, Tranny blew on our 2000 F350. We put a new(junkyard 69k miles) tranny in, and it will shift great up through the gears, but it will not downshift on its own. If I downshift on the collum, it works fine. It just won't downshift on its own. Is this something electronic? Any possibilities? It's a 4r100 4x4. Thanks for any advice.

 

It's all electronic. If it goes up it should go down. Something else must be wrong.

 

So are you saying it's the 'new' tranny, or something with the electronics controlling it. Are there sensors that control this outside of the tranny. Does this have a TCM, or is it all controlled by the ECM?

 

The engine and transmission are controlled by the PCM (Powertrain Control Module.) ECM is a GM term.

There are many sensors that affect the transmission. The throttle position sensors on the go pedal are very involved with shifting, as is the vehicle speed sensor on the rear axle.

The diagnose this you need a compatible scan tool that can read PID data so that you can see what the PCM is seeing and outputting.

 

your 100% sure all the electircal fittings and reattached and have sound connections right ???

i'd start there.. unplug and replug everything and make sure no connections got ruined during the tranny swap..

 

Cool thanks for the info. Sorry for all the seemingly dumb questions, but I don't understand automatics at all.

Most of my car/truck knowledge is with older trucks(pre-computer), and newer Audi/VWs. I have software that can read every module down to the door locks on Audi/VWs, but nothing for Fords. My friend bought a landscape company, and I've been doing Building/Equipment maintenance on the side for him this year. He has 2 F250s, 3 F350s, and a f450 currently, and is looking to get another f450 or f650 shortly. So I've had a crash course in 99-up superdutys over the summer.

I didn't want to get into this swap, so he had the guy from the junkyard do it. He's at a loss for an answer, so I'm gonna try to check it out tonight in person, before they take it to a shop.

Is there a good repair manual for these trucks online/CD you could recommend? Or a paper book, if that's the only option.