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My dad owns a 1953 M37. The transmission clunked out on it this week (3rd gear always clunked since he bought it from Fort Drum years ago, but this past week every gear began clunking). He's had a government-rebuilt M37B1 transmission sitting in the garage for awhile in anticipation of this happening.

So today, me, my dad, and a friend pulled out the old tranny and attempted to put the B1 one in. Everything was going fine until we had about an inch of space left between the bell housing and the transmission. The tranny just wouldn't go in any farther! We had it in gear and tried turning the propeller shaft on the back of it, and it seemed that it was meshing with the clutch and wouldn't move.

So we decided to pull the B1 transmission out, and noticed that compared to the original tranny that came with the truck, the taper on the engine-side shaft (can't think of the proper name for it right now) is a lot steeper and shallower than the original. We think[i/] this might be causing a problem with getting the thing to fit in the bushing in the clutch.

We don't have a grinding wheel on us right now to adjust this taper, but is there anything else we're missing?

If your bearings were severely worn on the old transmission, the clutch may not be properly aligned with the shaft (at least, that's what intuition tells me). When I installed mine I got it to about where you're at, and then held the clutch lever depressed while sliding the transmission in. This frees up the clutch disk and splines so that the clutch can be aligned by the new transmission shaft. I'm not sure if this is standard practice or not but it worked for me, doing an engine install by myself with no clutch alignment tool.