904 trans problem

Just rebuilt a 904 for a 71 scamp. I installed a B&M shift kit. The trans is going into reverse fine. But is slipping in forward gears to the point it hardly pulls itself. Fluid is starting to smell burned. Any help would be great. HELP

Are you sure you got all the O rings installed? I had a friends 904 on the trans dyno and it slipped really bad. He forgot to install one of the O rings on the input shaft.

Can you tell wich one ? for info,...

I'M quite sure. I have done a few of these. But I could have made a mistake. Is there a way to tell before pulling the trans? THANKS

It was years ago...but it was a small one on the input shaft.

Does anyone have an expanded drawing of the 904?

Sounds like you have major leakage at the rear clutch, remove the valve body and do an air check on the rear clutch passage. (good idea to do this at each rebuild)

THANKS