Ok got to go out and test some things with this tranny problem today.
under part throttle conditions I have no 3rd or 4th just revs, BUT if I step into the throttle a good bit I have all gears ............. .......go figure.

I made several different tests and it is always the same.....soft throttle no 3 or 4 .... hard throttle its just fine.

Got any ideas?
I sure don,t , never heard of anything like it.

 

Back when I had an auto mine did the complete opposite! Then again I also pretty much blew all the clutch packs for each gear .

I'd say check the fluid to see if it is bubbly or smells but I don't think you have the same problem.

How does it shift (when it does shift under heavier throttle), does it feel normal?

Maybe something is wrong in the valve body or a solenoid????

Dave

 

One other thing too, did you try scanning your pcm? I was looking through my service manual and some of the conditions show a trouble code appearing.

Dave