I'm in the process of rebuilding my T56. I'm down to reinstalling the countershaft extension and 5/6 driven gear. And reverse. When I put the countershaft extension assembly in and the reverse parts in, the reverse fork is hitting the top of 5th gear.

I've taken reverse and the countershaft extension off and back on about 4 times now. What am I over looking?

 

Figured it out. Had the thrust washer between the counter shaft and counter shaft extension backwards.