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Technical 39 3 Speed and Banjo Rear - shortening driveshaft Dallas?

Discussion in 'Traditional Hot Rods' started by 53OlderThanMe, Jan 19, 2015.

  1. I have a 39 3 speed and 39 banjo rear in my 31 Roadster. I want to keep the torque tube closed drive line. Got a few questions if you can help.

    1. To measure for the driveshaft, how far does it need to extend into the end of the u-joint coupler that connects it to end of tranny? There is a bolt holding one end of the u-joint to the tranny end, then driveshaft slides in the other end. I'm assuming it is supposed to go just to the end of the u-joint spline? Never seen one mounted...

    2. When I get the torque tube shortened do I need to try to keep the center bearing? If yes it would seem I would need to shorten the driveshaft and torque tube from both ends as the center of the driveshaft is a little larger diameter same as the splined ends. Is that right?

    3. Anybody know a good shop in Dallas area experienced in doing this correctly? I'm guessing I will get lots of blank stares if I just show up at a driveshaft shop.
  2. not sure if the shop up in Denton by you - Pientoes? does that - think maybe more on motors - try Rusty over at Dirty's Speed Shop...pretty good with chassie stuff and most anything else....are you running a banger motor?....if so that would make a neat thread....
    Rusty likes this.
  3. Thanks, running a SBC.
  4. Anderson
    Joined: Jan 27, 2003
    Posts: 6,473


  5. walter
    Joined: Nov 4, 2007
    Posts: 622


    I had a machine shop do mine in Wichita. I used two tubes and sectionded the center bearing back where it should be. I also had them cut the front of the shaft off and respline as well as cut the ring for the speed O gear. When it was done everything fit like Henry built it.
  6. Christom
    Joined: Nov 3, 2011
    Posts: 217


    There's several ways to do this job. Plenty of info on the HAMB on the subject. Also the Bishop/Tardell "How to Build a Traditional Hotrod" covers the subject. If you can't do the job yourself it would be good to show it to your machinist if he's not done one these before. I cut and welded the driveshaft with a sleeved joint for strength leaving the mint splines each end untouched as is. Used the rear spline collar pinned with metal-it to keep it nice and tight. I also kept the middle bearing in place. The required torque tube length was carefully measured between the trans and the rear flanges then cut and welded back together after checking the assembled driveshaft set up in place. In theory the tube should be shortened the same amount as the shaft but it pays to check the length of both - just in case - I got about .600" additional spline contact into the u-joint than it had before by checking the fit of the driveshaft. Hope that helps........
  7. I'm not sure how good this advice is.. but its on the topic of the torque tube, and not the shaft. If you can find a junk torque tube.. you might be able to cut the front belled part off, cut it square obviously.. and bolt that into the clam shells on the trans and measure from the end of the cut piece up to the mounting flange on the rear end. I have a junk '36 one that i'm thinking i can use.

    Once you know the length from the cut to the flange.. you can use that measurement to copy onto the full length tube.. then measure from the bell to the cut and copy that on.. and the distance left, take that out.

    Since most of the torque tubes as far as i'm aware have a tapered section, then a center bearing, then a flat section.. i'd take the cut piece out of the rear end flat section.

    Is this good advice? Has anyone else done it this way before?

    Obviously, if someone else can back up that this is indeed a sound solution.. the section you remove from the tube.. that same mount has to come out of the driveshaft. You could have a machine shop make a coupler tube that lets the driveshaft fit nicely inside it with absolutely a flyshit of space between it and the shaft.. and then when you cut the section out you can just weld the coupler to join the two together?

    I've never done one but i will be eventually.. and this seems like an alright way to do it.

    Also while i think of it.. when you weld the tube and shaft.. get a length of angle iron and tack that to your bench and then put the shaft / tube into it.. cut out a bit in the middle so you can get some weld all the way around. You can use this to clamp the shaft / tube solid.
  8. Dak Rat
    Joined: Mar 8, 2006
    Posts: 436

    Dak Rat

    28A--that sounds like a good idea--I'm going to try that with a front piece of junk T-tube I have.
  9. Anyone know if he is still in business? I've never gotten a response when calling the number and his voice mail is full. He sure would be convenient for me.
  10. Anderson
    Joined: Jan 27, 2003
    Posts: 6,473


    Granted I know him personally, but when I called him about some brakes back in November he answered immediately and had no problems.

    I know he's headed to the GNRS this weekend, so maybe try him again early next week.

    Posted using the Full Hot Rod H.A.M.B. App
    Last edited: Jan 22, 2015
  11. trucker1
    Joined: Sep 6, 2011
    Posts: 76


    If you use the later solid shaft your machinist can line up on the original splines and extend them toward the middle of the shaft giving you excess length on each end to trim off. This will give you good tight splines with a lot less slop.
  12. Once you work out how much you need to shorten the tube, the drive shaft is shortened the same amount, don't shorten the drive shaft from the front as there is a hardened section that the bearing runs on plus the circlip groove, shorten from the rear, have a machine shop cut a new spline and just drill a new hole for the retaining pin for the diff coupling. Don't need the center bearing on a short wheel base car, check out my 32 roadster build thread post #57 to #64 on how I shortened mine.
  13. edwardlloyd
    Joined: Aug 2, 2003
    Posts: 2,067

    from Germany

    Assemble trans mount, axle, torque tube and rear axle in your chassis and set everything at ride height. You dont even have to fit the drive shaft yet. Simply measure from the center hole in the rear crossmember to the center bolt in the rear spring. That's how much you're going to shorten both the tube and the drive shaft. Shorten both at the axle end. You don't need to re spline the rear. Just turn it down til the coupler slides in place and weld up. Make sure you've left enough space inside for the pinion shaft to slide in far enough to refit the pin. It's very important that both get shortened exactly the same amount otherwise you'll never assemble your speedometer drive.
    Cut the tube a few inches back from the flange and keep it clocked and keep it true. Any proper machine shop can do this.
    Now you can shorten, heat and bend your super long '39 bones or use '42-48 rear bones which sometimes fit perfectly or need only a little modification. If possible use the neat '42-'48 T-piece brake line bracket and run the lines down the inside of each bone.
    Last edited: Jan 25, 2015
  14. boo
    Joined: Jul 6, 2005
    Posts: 557

    from stuart,fl.

    am doing this right now for my 27 T. have a columbia rear that i had Stoksbery bulit proof and change to 4:11 gears, the gears were the early 'more splines' pinion. i cut down a 48 tork tube, clambing the pieces w/3 pieces of angle iron to keep straight while welding. i am using a drive shaft from a 34 rear, they are a tube ' approx 1 1/2 dia', easy to put in lathe and trim off end and then cut tube and slip over end and weld. this is my 3rd time w/this setup.
  15. brokenspoke
    Joined: Jul 26, 2005
    Posts: 2,911


    Rusty knows his stuff....
    Rusty likes this.
  16. Rusty from Dirtys already finished it for me. I will post some pictures later of how he taught me to measure it.
    Rusty likes this.
  17. 31 Chopped Coupe
    Joined: Aug 24, 2014
    Posts: 97

    31 Chopped Coupe

    Soon please, and lots of pics. I'm at that same step. thanks
  18. manyolcars
    Joined: Mar 30, 2001
    Posts: 8,420


    I shortened the front and got a fresh surface for the center bearing to run on
  19. 31 Chopped Coupe
    Joined: Aug 24, 2014
    Posts: 97

    31 Chopped Coupe

  20. Lone Star Mopar
    Joined: Nov 2, 2005
    Posts: 3,070

    Lone Star Mopar

    Rusty has been posting pics on IG shortening a torque tube this week.
  21. That's mine, didn't want to post Rustys pictures without his permission.
  22. cool.....sorta was afraid I'd miss spoke......

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