The Stovebolt Site Forums The Parking Lot Tons 'o Fun 2 to 1 piece driveshaft

Has anyone converted their truck from the original two piece propeller shaft to a single piece drive shaft? Looking to eliminate the carrier and some weight as well. I need to overhaul the entire driveshaft anyways and it looks like it would break even if I converted it. Just looking for opinions...

I went to a one-piece drive shaft in my 47 3600, but I added a Gear Venders Overdrive to the back of my SM420. It adds about 14" to the back of the trany so the drive shaft is not as long as it would have been without it. I have the open output housing for a SM420 if someone needs it. I was going to go that route but decided to go with an overdrive instead.

Reinventing the wheel is usually not a good idea. If a 1 piece driveline would be correct, why didn't they manufacture it that way in the first place? You will need to go with a much larger diameter tube and very expensive yokes and U joints to get the required stiffness and resistance to vibration. The U joint geometry will get very tricky, also.
Jerry

I feel like since this is now used very much like a lighter duty truck, that going to a one piece 3 to 4in shaft would be able to work just fine as far as stiffness goes. And geometrically speaking the U joints would receive much less stress due to a shallower angle. I intend to swap to a 14 bolt anyways so I can also correct for the angle there as well. The only thing I would really absolutely have to do is replace the bearing for the output shaft of the transmission since that will be seeing more side loading than before.

Opinions are like "noses"- - - -everybody's got one, and some of them are pretty smelly. Hands-on experience, on the other hand, is a lot more scarce, and is usually ignored.
Jerry

Jerry ....

CBall -- I use my 3804 about like everyone else uses their 3100's...

But ..

I run a 261, 17-inch wheels and I did the 4.11 conversion on the rear axle center section. I'm still running Huck brakes, 17-inch bias ply tubed tires. I can run 65 MPH all day long. If you want to go to the trouble of converting to a 14-bolt, then fine -- that's great! Have at it and we'll support you all the way. I'm just backing up what Jerry is trying to tell you that the 1-ton AD set up is far more amenable to modern roads than the the 3100 AD trucks ... Easier to convert.

Bottom line -- you are in luck that you have a 1-ton (I assume ...) The factory set up is darn good and simple to tweak.

Thanks!
John

I did it on my 3/4 ton. I originally LS swapped it but used the entire stock driveline with torque tube. When I added a 319 with the borg electric OD I needed to have a driveshaft made. I priced out the 2 piece and choked. I asked the place to do a one piece shaft and they were very reluctant. The guy said it was like 2” too long out of his comfort zone for a 1 piece shaft. He said he would so it for me with no guarantees or i could do a 4” aluminum shaft no problem. I thought he was stupid and I was smart because ive done wayyyy sketchier things with no problems. So i did a TON of research and turns out the man knew his stuff! It was JUST a little too long for the rated tube wall diameter/thickness/ length BUT I ran the calculations multiple times on the max driveshaft RPM that I planned on spinning and it was technically still in the “safe zone” but it was right on edge. Now my truck is ALL stock steering and brakes so I dont drive it like a maniac and my cruise speed is 65-70mph so knowing that my driveshaft is technically not rated to go much faster actually sticks in my mind and keeps me at a safer speed. Ive run it at 80mph a few times just fine and its been in the truck zero issues for at least 3yrs now. This is all just food for thought. I will say I LEARNED A LOT by doin all that research. Learned drive shaft tubes are seldom “round”, learned about tube deflection and that the shaft actually turns itself into a jump rope at a certain pre determined RPM, learned that the more weight in the shaft the more exaggerated stress it puts on the u-joints and learned how to really calculate the most important thing in figuring a driveshaft…..RPM.

I will PM you regarding the housing.