The Stovebolt Site Forums The Shop Area Driveline slip spline driveshaft?

I am putting a granny four speed transmission in my 1959 3100 pickup. The transmission came out of a 1959 3800. I am wanting to use a slip spline driveshaft instead of a two piece shaft with a carrier bearing. I told the old man that I always deal with at the parts store in town and he acted like what I was going to do was unheard of. He has been in business for longer than I can remember and really knows his stuff so that kind of worried me. Have any of you done this? Did chevy do this on their short wheel base trucks originally when outfitted with a four speed or did they always use a two piece driveshaft with a carrier bearing?
Thanks a lot,
Gene

On my 58 longbox, the three speed trans has a single shaft, and the 4 speed has a 2 piece with a hanger bearing.
My 1960 shortbox has a single with a three speed. I would assume a single with a 4 speed also.

Looks like all short beds had a one piece based on this literature. Scroll to page 49 on this link for details.

https://gmheritagecenter.com/docs/g...olet-Truck.pdf?zoom_highlight=1959+truck

Matt

Thanks guys. I am going to get a driveshaft built today. I can't wait to get that three speed out of there!

I have owned and maintained trucks for over 50 years. The purpose of a two piece drive shaft is to absorb more torque. That is why the 4 speed had a 2 piece with a center bearing. If you are not going to be starting off with heavy loads, a one piece drive shaft will work. If you plan on untracking heavy loads, stay with a 2 piece drive shaft. One piece drive shafts are also more vulnerable to vibrations.

OK, finally got the 4 speed in the truck. I got the driveshaft built and then it started raining. When they finally forecasted a dry day, I borrowed a transmission jack, slid a piece of plywood under the truck and swapped them out in the back yard. It was the first time I have ever put a transmission in by myself and a sm420 is a heavy son of a gun. I was proud to get it in there! It is like having a new truck now. Second gear is a little lower than first on the three speed. Third is a little higher than second on the three speed. And high gear is 1:1 on both of them. Another thing that I really like is reverse is the same as compound. Reverse was way to high with the three speed because I installed a 3.38 rear end last year. My old three speed made a little noise going down the road and the new transmission is quiet at 65 mph. It also has a good hand brake so I can quit scotching the wheel every time I park on a hill. This was the biggest improvement that I have made since I got the truck.