The Stovebolt Site Forums The Shop Area Engine Shop 3 speed or 4??

Have to put a new transmission in my '51 GMC 1/2 ton long bed. It presently has a 3 speed but I was wondering about a 4 speed. I have heard that you need a different u-joint for the 4 speed and there are abit hard to find. Since I have a a long bed and I have 2 u-joints I was wondering if I need t replace both or is only 1 that is different?
Any preferences between the 3 and 4 speed?
Tom

thomas,
The transmission is more according to what you like. The three speed of course would be easier to install since you have the parts for it. My 1/2 ton had a four speed and I like it because it is sync in the top three gears. You would have to find a four speed from a half ton truck that would have the rear piece for the ball. My U-joint went bad on mine so I got a u-joint from a 3/4 ton. Had the rear part of the joint machined out and the rear part of a three speed joint welded in. Much more heavy duty than original joint.
The early 3/4 ton Chevy trucks also had enclosed driveshaft between transmission and carrier bearing. I'm not sure up to what year they were made that way though, at least I think till '51 or so. I think the transmission would also work from these trucks, but you would still have to come up with a u-joint. I hope this will help.

Thomas,

Any '48 to '54 1/2-ton 4-speed should be a direct bolt-in.

The '48-'53 3/4-ton 4-speed also had the enclosed u-joint, and should work;

The 4-speed from the larger trucks had open driveshafts, and aside from that, are the same tranny.

Your limiting factor here is finding something that will adapt to your existing tourqe tube rear.

Is your 3-speed beyond re-build?

Unless you want to keep it original-like I would go with a saginaw or better a t-5. Supposing you're using the original 228 stock. When the joints went out on mine they shreded the bells so I just tore the whole truck down to rebuild . but seriously after driving mine as long as I did I was ready for that od. Should be an easy swap, you'll get your floor shifter too. Pick up a rear axle (125-150 bucks here) and get a driveshaft built (about the same as the rear) and a s-10 t-5 (I got one for $175, a good '95). Look into it if it's what you want. Should be great with that jimmy motor. Seeya

I changed the 3 to a 4speed on my 54 3/4 ton just because i wouldnt have to deal with the linkage for the 3 speed and I found a nice 4speed for $100.I also like the floorshifting because it feels more direct. I didnt have the driveshaft problem because mine is not enclosed. good luck