1939 clutch input shaft 3 spd vs 4 spd

[NCSUDucker]

Question for you guys. We tried the MMO in the cylinders but appears the rings are shot with compression still real low in two cylinders (25/30) and moderately low in the remaining 6 (65 to 75). I was going to have it rebuilt but came across a recently very nicely built 59a at a decent price. He's got it on the stand right now but currently doesn't have a clutch and is happy to put one on. Do the 39 4 speed (1 ton) and 3 speed have the same size input shaft?

Or better yet, just trying to make sure the 59a is going to be compatible with the 39 4spd if that makes it easier to answer.

Thanks,
Brad

[cas3]

Fords up to 48 share the same size input shaft. Trucks, a few years more.

[Mac VP]

The truck 4 speed transmissions have the same splines, shaft length, and spline diameter as the 3 speed input shafts…….from 1932 through at least 1948. The truck input stayed the same up through 1952 types. The passenger car input shaft changed to the smaller 1” diameter with the new 1949 models.

[NCSUDucker]

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Originally Posted by Mac VP

The truck 4 speed transmissions have the same splines, shaft length, and spline diameter as the 3 speed input shafts…….from 1932 through at least 1948. The truck input stayed the same up through 1952 types. The passenger car input shaft changed to the smaller 1” diameter with the new 1949 models.

Thank you!