I'm planning to build my own driveshafts for the 84 SAS'd Bronco out of square tubing, and would like to hear any input from othersthat have done this mod. The stock F-350 shafts are either too long or too short, and don't have very much motion for the Bronco. i picked up two pieces of tubing, one is 2"x2"x1/4"thick seamless receiver hitch square tubing, the other is 1.5"x1.5"x1/4"thick seamless. I'll do awrite-up on the actual build once i get the time, but am still looking at options for end yokes. i don't like the short ds yokes on the F-350 shafts, so looking at using some longer ones from the local tractor supply. these are used for pto shafts on shredders and such. My big problem is figuring out what length to cut the tubing, so the ds doesn't bottom out or slip apart. i found thru fitment of the two pieces that at least 12" of the 1.5" tubing is needed inside the 2" tubing to get good engagement without much wobble. My rear ds needs to be about 28"-29" total length, while the front ds needs to be 35"-36" long. these are measured while the rig is at rest. JSM84

I found this good write-up on how to build one and how to measure for it :

http://board.marlincrawler.com/index.php?t...uare+driveshaft

Hmmmmm Im not sure how that will work for ya . At road speed its probably going to shake a bit . Round is stronger than square because of the surface area thats why you never see square ones on everyday drivers . I guess let us know how it works out

Ive seen them on hardcore rock crawlers with very good results. They would be wobbly a bit at highway speed but perfect for the mud drags!!!

Yes, the 84 is for offroad use only and is trailered to any mud drags or rock crawling events. i doubt it will seldom get over 10 mph while rock crawling. I'll eventually get some custom shafts made for the mud drags if these don't work out. JSM84

I'm also debating on whether or not use a double-cardan (DC) joint on either shaft.

i would take a 350 drive shaft that is too long and get a round tube that will slide over this and weld the two together. I dont think square will distribute the torque very well, especially if it gets in a bind. i had a friend of mine make a drive shaft like above for a car pushing out about 600hp. Just remember whatever tube you use on the outside is going to take all of the twist.

It would be no good on a street car but like JSM said its very cheap to make and its not going to be driven at very high speeds. They built square tube driveshafts on the bottom drawer buggy on extreme 4x4. these tubes will support the weight of the vehicle which happens quite often while rockcrawling. these are hardcore driveshafts make for hardcore wheeling and they work great. They bind grind and clank as well as vibrate on the road. But they are not for the road so its all good.

I got the rear driveshaft built over the weekend. Here's a link to the album at SFO:

http://www.supermotors.net/vehicles/registry/1133/30189-4

And a pic of the finished shaft:

That looks beefy, how tight is it? Much slop?

It's quite snug, with very little wobble at all. The smaller 1.5" tubing is cut to about 16", so there's over 12" of it inside the 2" tubing. it still slides rather easy even without grease, but I'll grease it before installing it under the Bronco, JSM84