The Stovebolt Site Forums The Shop Area Driveline Replace SM420 Floor Shift Trans. with 3 Speed Column Shift Trans.

I am considering replacing the floor shift SM420 4-speed transmission in my 1952 3100 for a column shift 3-speed transmission.
Question: What difference(s) if any, are the 1948-'53 3100 3-speed transmissions VS the 1949-'54 CAR 3-speed transmissions?
The reason for this Question is: A CAR Transmission in good/not abused condition will Probably be easier to find.

Welcome to the Stovebolt

That seems like a lot of work for no gain of any kind other than floor space, both transmissions are direct drive with 1:1 high gear ratio. The SM-420 is bullet proof behind a 6-cylinder and you'd drive it like a 3-speed, starting off in 2nd gear all the time.

Mike B

I realize that this doesn't answer your question but first gear in a three speed is higher than second gear in your 4 speed. Reverse in the 4 speed is the same as granny which is great when you go to back up. In the three speed, reverse is the same as first gear which is pretty fast. It seems like every vehicle I had as a kid was a 3 on the tree and I always wished that it was a four speed. I swapped out the 3 speed in my truck for a sm420 and it is like driving a completely different truck now. That is just my opinion but I would never swap a good sm420 for a three speed.

Can someone suggest a Website that could increase my chances of getting the answer to my question? Thanks

Stovebolt.com is the best site for finding info about your truck .... patience grasshopper
to investigate car transmissions, maybe check the shop manuals here - also check the "resto-pak" PDF for 52 to find what was available and dimensions

1st question is, why are you considering the change?
then, what makes you think the era car trans would be easier to find?
do you have all the shifter parts, including a column that has provision for mounting the lever and shift box on the lower column?
have the correct rods to mate any 3 speed to that shift box?
usually the car vs truck trans have differences is those shifting parts, so you're looking for parts from different places - easier to find someone like Gene who took the 3 spd out of their truck so you get everything involved to do the conversion all at once and you know they'll mate

Bill

My suggestion is to learn how to search our website.
It seems that a truck tranny will be much easier and stronger. A car tranny will not be easier to find and they were used more and abused more by Hot Rodders. We didn't buy trucks till much later in life.

According to the bell housing bolt pattern guide that pre68Dave has provided on this site: Passenger cars of that era had a different bolt pattern than trucks.
Fred