my 95' poweroke has a fresh rebuilt auto tranny and acts really weird when I start it up .... like when I start it up and drive it (I live in the country part of GA, so I have long roads) and when I pull it out it will shift fine until I get to overdrive.... its almost like the clutches inside are not grabbing it will tack up to 2400rpms going up a hill going 55 then( it loses a lot of speed going up the hill still taking 2400 rpms) when I come over the hill it will still tack the same and it gains speed and I don't hear any shifting.... then about 4miles down the road it will shift and lock down but it wont do it if I let the truck warm up either ... its really weird hard to explain but would anyone have any ideas

 

Im sure you have checked the fluid level, now check for codes.

 

I agree 100%

 

Who rebuilt it? I'd take it back and voice your concerns with them...

 

There are a ton of threads to read on e40d issues. I was in the same boat only i had hard shifting off the hop and then similar conditions to yours.... mine was the third brake light was burnt out! Read the threads and pull codes and report back.