The Stovebolt Site Forums The Shop Area Driveline Is this 3 Speed correct? 55.1 3100

Trying to help my friend ID the transmission in his 1955 first series 3104 pickup. So far everything looks correct but this trans looks wrong to me. I haven't had a 3 speed in a long time, and what I had was a 54 that had a torque tube. I know that my tailshaft housing was completely different. Much shorter. I was under the impression, that as the 1955.1 supplement states, that the 54 trans was only modified to be able to use the hotchkiss type u-joint. This trans looks like it would be of a later type.

The case casting number is 3845122, and the tailshaft housing number is 3707196 if I'm reading them right.

That housing casting number says it's a 55-57 Passenger/Corvette tranny. This is an excerpt from this page. 3707195 is a 55-57 Extension housing for all 3 speeds except OD & Heavy Duty. Part #4.317 in the same link above.

Thanks, Kevin. That answers that!

Isn't that trans a car/truck hybrid? I thought the car transmission cases had bolts coming in from the back side top and bottom, while that one appears to have threaded bottom mounting holes with the lower bolts coming through from the clutch side. Maybe a car output shaft and a long extension housing got grafted onto a truck main housing?
Jerry

The main housing casting number comes back as a car tranny, so maybe it's a car tranny with a truck tailshaft.
It appears the mounting bolts may be the same for both car and truck. Why would GM go to the trouble to make them different?

I might have the Muncie and Saginaw 4 speeds in mind, not the 318 and 319 3 speeds. I remember having to use bolts and nuts on some applications due to the lack of threads in the lower bell housing bolt holes or the transmission cases.
Jerry

That is the correct truck transmission for that vehicle. Both cars and trucks used the 122 case casting number and the long extension housing in that period.
Fred

I have now located two other 1955.1 Chevrolet 3100's with this identical transmission. I think it is correct. It's just so much different than the 54 trans that I had to question it. I would have thought this deserved more than a few paragraphs of poor description in the 1955 First series shop manual supplement.

I'm surprised you located that many that haven't been modified. The 55.1 is sort of an anomaly as it was only a partial year build and contained components from the previous year and changes like the open driveline on the next series. GM used the SM318 identifier on way too many transmissions in my opinion. 48-54 with a torque tube, 55-62 in trucks and 55-57 in cars with the long tailshaft, 58-64 in cars and 64-67 in trucks with the short tailshaft. It's no wonder it's confusing.
Fred

I have that same tranny in my 55.1. Just for the record.

I'm in the process of replacing it with a T5 behind the 235.
If anyone happens to need this 3sp, shoot me a PM.

Don