I picked up this automatic 3.4 T100 a few weeks ago to replace an old Ford that needed more work than it was worth. The guy sold it to me cheap because he claimed it needed a transmission because it wasn't shifting into overdrive. I test drove it and it seemed perfectly fine to me so of course I bought it. I've been driving it semi regularly and I would say 80% of the time the transmission behaves perfectly fine and the other 20% it gives me issues. Sometimes I will get a couple miles down the road and it'll drop to 3rd and sometimes it'll go back to 4th and sometimes it won't. Sometimes it'll have a little fit hunting between 3rd and 4th and I'll just hit the OD off. At no point am I getting a check engine and the OD light does not blink.

I've read about the shift solenoids and at this point I'm leaning toward that but I've also read that a flashing OD light usually accompanies that issue. Possibly a sensor issue?

 

I think I've figured it out... Now just to find a replacement that doesn't cost an arm and a leg