I am back but not with my own vehicle this time.

A friend of mine has a 1970 Mustang with a C4. When in reverse it runs fine while letting it idle. But when stepping on the gas, the transmission chatters.

She had it rebuilt a long time ago and has done it since then. I suspect the rebuilder left out a friction disc/plate combo, hence a slight gap so nothing meshes completely.

Since it works, I/she have no plans to do anyting but I wanted to ask ya'lls opinion. Am I missing anything? Could there possibly be an external adjustment?

Appreciate the help.

Brad Shanks
a.k.a Spyfox.

 

My guess would be a problem with the reverse band. Sometimes the end of the band can crack causing what you describe. However I would have thought it would have broken by now if that was the case.
It may be that the reverse needs adjusted which could also cause the problem.
I am no trans expert so just a best guess.