I just had my trans rebuilt- the builder swears I should use conventional oil because of "heat transferance" problems with synthetics.

This seems contrary to my past experience, plus what I've heard from others. Wear may be
better, but this trans got real hard to downshift from 4th to 3rd on my first weekend out with it.

Anybody got good or bad experience using synthetics with a "7" trans ? I know they are a little delicate- I'm leery of experimenting.

Thanks for all feedback !