From303

First, I should explain, I am not a mechanic. My Dad is doing all of the work and I was just looking for a way to help.

It's a 1997 Cavalier and the engine went out. My Dad rebuilt it with the help of a machine shop and has it put back together now. Except when you try to go forward, the engine revs but it doesn't gain much speed. If you keep at it, slowly it will get up to 35 and even 50 miles per hour. Once you are there, it goes smooth but you can never keep up with traffic getting to those speeds. He said he can tell from the sounds that it's in the transmission. Which is an automatic.

Any suggestions?

From303

Oh and I didn't notice any transmission issues before the engine went out.

tech2

torque convertor stator maybe? if it doesn't lock and hold you will have poor torque multiplication, but it will cruise just fine.

From303

I looked that up on howstuffworks and that makes a lot of sense! I recommended it to him and he said he believes the transmission bands need to be adjusted. Do you think that could be the problem instead?

From what I read, your idea makes the most sense. I'm not gonna argue with that man that's doing the work though

tech2

nope. Maybe if the transmission was from 40 years ago or from another manufacturer that actually require band adjustment.
is the kickdown/tv cable adjusted properly or is it fully electronic? this is an important input for sensing load?