just had my th 400 rebuilt with a full manual reverse valve body and art carr shifter

when i put it into a forward gear, it goes right in, no problem

but when i put it in reverse it hesitates for a few (4 or so) seconds.

the art carr isn't super tight, so maybe i need to adjust it a little more, but like i said it goes in forward gears right away.

so, what are the chances it could be something within the tranny?

thanks

Sounds like an internal problem to me.
Have you checked line pressure?