For months, i was experiencing a shifting problem around 40-50 mph. Tranny would shift too early and bog down or go back and forth between gears. I thought it was just b/c the truck has 190k miles.
Couple weeks ago it wouldn't start and I got no "wait to start" light. Troubleshot it to bad starter contacts. So after replacing the starter, my tranny magically runs perfectly. Since when does a starter fix a shifting problem? I'm beyond stumped. And there's no way its a coincidence because it literally fixed it immediately after I started the truck with the new starter, and the shift problem was going on for like 8 months.

if you're an expert or you've seen this before, i would love an answer. thanks

 

Perhaps just weak or dirty connections ? I have some weird stuff going on with my truck electrically too.. Fuel gauge works when it wants too and when it does work the transmission shifts fine, when it dont work the transmission goes into limp mode...

 

I had the same trouble with mine and it turned out to be a broken wire in the harness going to the trans. This started on mine at about 100000 miles, trans shop fixed wire and no more problems since then. Dealer wanted $3000 plus to rebuild trans.

 

I have heard that weak starter contacts cause electrial noise that messes with the tranny. since i have manuel i have not had problem

 

I think that whan you removed the starter you disconnected both battery grounds. When reinstalling them you got a better connection and the electrical noise that made your tranny shift erratically is being filtered by the battery again.
In my experience with all modern cars and trucks if you experience some erratic behavior start with cleaning the battery connectors and posts.
Solves approx. 50-60% of the problems I encounter.
HTH

AlpineRAM