Am in process of getting 5-speed gear box back together after re-build. Tried installing rear extension case to main transmission case but either one or both of the rear bearings (main shaft or lay shaft) seemed to bind as I torqued nuts/bolts to 18 ft-lb. With bolts untorqued, gear box rotated freely.

Haynes manual calls out just hammer-tapping rear case onto transmission case, which I did. Both bearings are tight press-fit into rear case. Is there a right/wrong orientation of rear bearings? Both Haynes and Fiat_Shop_Manual do not refer to anything special.

Appreciate your input.

Might be tighter than when you took it apart due to wear, but should not bind. I would check to make sure the bearings are pressed in to the tranny "straight". Also did you put some tranny oil on the shafts as you slid them together. It does help some.
r/

Thanks.

The solution was to put the rear housing in the oven at 200 degF for 30 min and it slipped on perfectly. My crude calculations the dia. of holes in casing increased in the housing by 0.002" to 0.003" through heating which was more than enough to get the bearings to slip on.

Maybe there was a burr where the bearings slide into? I've rebuilt dozens of gearboxes and never had this problem, so it seems kind of strange, but hey, if it works now, all the better