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TECH REQUEST: Cutting and shortening a driveshaft at home.

Discussion in 'The Hokey Ass Message Board' started by TINGLER, Mar 8, 2006.

  1. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    Yeah, I've done my share over the years with no ill affects.

    You can use a wrap around or make one.
    This will give you an accurate square line to cut the tube....But I use a plumber/fitter pipe cutter to get a square accurate cut. You will have to file out the inside burr (careful it's sharp) so that the casting can slide back in. These things are "close" to being self centering. I use 2 long staight rods to eye ball the indexing between the front yoke and the rear U joint. It's worked for me.

    I wouldn't try to talk someone, who is nervous about it, into trying it but what is the worst that can happen (if you are a competent welder)???...You'll get a vibration. Really! That's it. If you screw it up, you'll get a vibration. It's not going to explode sending you off the road into that mini-van full of kids. If it vibrates take it out and see if it can be balanced. If it can't, find out what you did wrong. None of mine have had any vibrations and performed well for as long as I had the car. I sent the last one out due to time constraints. Shortened and balanced...100 bucks wholesale.

    Just don't ask me to take an automatic trans apart!:D

    40 years ago a buddy of mine swapped a SBF into a 6cyl Comet one weekend. Sunday night he discovers the U joints don't interchange. He slid the 6cyl rear shaft inside the V8 front shaft, adjusted the length and then brazed the two together. Yes brazed. It got him to work and back on Monday until he could get it done right. Yes we called him an idiot.
     
  2. Saw references to Dialing elsewhere, is a good thing if you want, but not necessary. Checking the end of the tube after the cut with a square should suffice. If dialing, check the end of the tube after the cut, then whack the yoke in, the centering is automatic.

    Here’ a “TECH WITHIN A TECH”
    BALANCE YOUR DRIVESHAFT TECH
    It’s not my intention to steal this thread, but didn’t see where anybody explained the balancing process in coherent detail.

    If you are one that don’t like the ‘look’ of the time honored ‘worm clamp process’, here’s a ‘higher-tech’ way for those that really (feel a need to have) a balanced driveshaft. It’s my opinion that most are within acceptable limits already.

    Support two straight-edges about 3 feet apart, parallel and level to each other. Clean rusty scale and mud globs from the tube. Lay the driveshaft on the straight-edges. Gently roll it back and forth. If it doesn’t have a tendency to stop in one place, it’s already balanced good enough for me. If it stops, mark the top center with chalk, move it around, play with it again, and see if it stops in the same relative position as before. If it does, it has a heavy spot. Tape a flat washer at the top of the tube, then repeat the procedure. Subsequent results will be a combination, possibly you’ll need a heavier, or lighter washer to get the thing where it will roll gently, with no apparent tendency to stop. Attach the washer. Braze, solder, weld, Epoxy, or even drill and tap for a screw. Stencil for lookers, "Balanced by (insert your name), then brag to all comers that you did your own………. :D
     
  3. plymouth_man
    Joined: Feb 12, 2006
    Posts: 50

    plymouth_man
    Member
    from WI.

    I myself,would cut the back of the drive shaft,not the front. If your weld would happen to come apart,I would rather have it fall out the back,than haveing it fall out from the front. have you ever had the u joints break in front? HOLD on,were going for a ride. not fun.
     
  4. Flatdog
    Joined: Jan 31, 2003
    Posts: 1,285

    Flatdog
    Member Emeritus

    You have described a good way to check a driveshaft for straighness not balance.
     
  5. Killer
    Joined: Jul 5, 2001
    Posts: 1,567

    Killer
    Member

    the cut on the tube doesn't have to be perfect, the yokes are pretty much self aligning...

    cut the weld and bang one out, you'll see what I mean.
     
  6. HemiRambler
    Joined: Aug 26, 2005
    Posts: 4,144

    HemiRambler
    Member

    No, that's not exactly true. If you were to do as I suggested at the MIDDLE of the shaft then yes I agree - you could detect a warped shaft. BUT, what I am saying is to check it at the ends (preferably the transmission end) - the imbalance (if present) will cause a VIBRATION - the vibration manifests itself as a "wobble" with the heavy side whiping around some. The shaft CAN be straight as an arrow and still wobble as a result of imbalance. It is THAT wobble that you are trying to detect. If your shaft is bent you don't need to spin it to detect that although spinning could help diagnose that as well, but consider this - let's "pretend" that the shaft is bent ONLY in THE MIDDLE but manufactured somehow such that it's still in balance. It would PASS this test ON THE ENDS. The driveshaft on my '37 truck is exactly this way - the center is damaged - actually embarassingly so - but it is still in balance and performs well - no vibration doesn't eat ujoints etc etc. What we are concerned with here is that IF it is IN BALANCE the ENDS will spin true - if not they will tend to wobble - regardless of what the center does (to a point).


     
  7. Flatdog
    Joined: Jan 31, 2003
    Posts: 1,285

    Flatdog
    Member Emeritus

    I have very mixed feeling about this post.I have straightened many driveshaft in a car on a lift with heat and shrink meathod.Some of the thing in this tread are Dangerous.If you are not real sure about your skills this is not a car part you should be playing with.
     
  8. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,514

    Digger_Dave
    Member

    Strange you should mention the drive shaft u joint failing at the front.

    Last night on "Mythbusters" (Discovery Channel) they set about to find out if the FRONT u joint on the drive shaft, FAILED and the front of the drive shaft dropped to the ground catching a pot hole; would it "pole vault" the car end over end??

    It took a couple of tries; but all that happened was the drive shaft folded over locked the rear tires up and rammed it's way through the trunk floor. (BTW - it was a '60's something Plymouth! -4 door hardtop )

    Myth Busted.
     
  9. Flatdog
    Joined: Jan 31, 2003
    Posts: 1,285

    Flatdog
    Member Emeritus

    Dave don't believe everything you see on TV .In the 60 we had a Chevy 2 pole vault on rt 287 racing, killed the passenger.Driver did some jail time.
     
  10. Mr 42
    Joined: Mar 27, 2003
    Posts: 1,208

    Mr 42
    Member
    from Sweden

    Ive done some shortening myself, on the workbench.
    No problem at all. even built my own from scratch using a thinwall tube (not exhaust ;-))

    Usually im using a plumber/fitter pipe cutter to get the ends 90 degrees.

    No problem with vibrations at all.

    So it can be done if you are unsure about you skills, build a loop around the driveshaft to catch it if it brake.

    Just my tre öre :)
     
  11. Flat Ernie
    Joined: Jun 5, 2002
    Posts: 8,410

    Flat Ernie
    Tech Editor

    I've done it just as described here - cut off & clean up the rear yoke, cut the tube (I actually used a hacksaw!:eek: ), grind old weld off yoke, tap in, square/phase w/other yoke, 3-4 tacks, finish weld while turning in V-block/angle-iron.

    Last one I did, I took to a driveline shop several years later to have it balanced (because they were in the warehouse right behind me - convenience, nothing more) - they said it required no weight & when I told 'em I did it myself on the bench, they freaked!:D (rather be lucky than good anyday!;) )

    I've done a few & have also used the hose clamp method described above to balance the one or two that did have a low-speed vibe...most were fine.
     
  12. Powerband
    Joined: Nov 10, 2004
    Posts: 542

    Powerband

    Very interesting ...

    Last fall I swapped out the 3OTT for a factory option Dagenham 4 spd in my 6cyl. Falcon "Pursuit 170" wagon. Everythings hunky dory with the swap and I got a correct length driveshaft from a forum member (Thanks again). Problem is it vibrates to the point the mirrors fuzz and my ass falls asleep - above 45 MPH. I took it to a place recommended here, (Conneticut Driveshaft). They said it "is out .030 and can't be balanced", wanted $200 to retube it.

    What you think?. I didn't think 30 thousandth's sounded like a lot on @ 5' of shaft but the balance vs trueness controversy, still is debatable. I figured I'd try the clamp-balancing before forking over 200 clams. I still haven't acted on this but I did mention the SS band clamp idea to the tech and got a blank stare. Am I being shafted or what?.

    [​IMG]

    Powerband :cool:
    [​IMG]
     
  13. fordcpe
    Joined: Nov 4, 2005
    Posts: 636

    fordcpe
    Member

    I use a big pipe cutter( like you use to cut brake lines but bigger) to cut the shaft to length I also cut rear end s this way to shorten then. I use a lathe to true the yokes or ends for rear ends. I then use my angle finder to put the yoke in line with each other than mount in car and use dial indicator to get no run out.Weld and check Darrell
     
  14. atch
    Joined: Sep 3, 2002
    Posts: 4,407

    atch
    Member

    i don't know whether your shaft can be balanced or not. what i do know is that i'd look for another shaft and have it shortened before i'd shell out 200 bux to have a new tube put in yours.

    as someone mentioned above, the going price for work like this is a case of beer. at least i'm one of the fortunate ones who has a friend with a shop that will do this for his friends.

    that aside, when i needed a driveshaft for clarence ('48 f-1 w/ 283/350 & 8" rear) i put the yoke into the rear of the tranny to the point where it had obviously been running before, based on rust vs. shiney, and measured from that yoke to the rear yoke. this after carefully phasing the yokes. then i went to an old-fashioned boneyard that takes the driveshaft out of any vehicles headed for the crusher. they are stored in a van out in the back. i had decided that if i could find a driveshaft with the right sized yokes and a certain length (+/- 1/8") that it would fit without modification. in the pile of a hundred or two hundred shafts i found two that would work. i picked the best looking one and bought it for $10-15; i can't remember exactly how much. that was in 1991 missouri dollars. don't know what it would cost today. anyway, bought two new u-joints, installed it, and have driven around the world several times since. well, not actually, but clarence has wracked up LOTS of miles since then, with nary a glitch.
     
  15. Digger_Dave
    Joined: Apr 10, 2001
    Posts: 2,514

    Digger_Dave
    Member

    F.D. - Seeing as how the car they used on the Myth Busters program was probably a LOT heavier than a Chevy 2; the drive shaft just folded.

    The car was operated by remote control (from a pick-up driving along side) and a camera was mounted under the car. (remote; high speed/slow motion)

    They had dug a "pothole" that the front end of the driveshaft caught at 50 MPH; the car barely slowed down.

    BTW - did I mention I'm a fan of drive shaft safety hoops? (especially when racing)
     
  16. Flatdog
    Joined: Jan 31, 2003
    Posts: 1,285

    Flatdog
    Member Emeritus

    Power, if the shaft is true, balance is ok.Balance will NOT fix trueness.I think I have more experence that any on the board. 30 year road testing and and trouble shooting drive line problems in the real world.
     
  17. Flatdog
    Joined: Jan 31, 2003
    Posts: 1,285

    Flatdog
    Member Emeritus

    Dave much heavier car and longer shaft than Nova.God I wish I could spell and type.-
     
  18. 57JoeFoMoPar
    Joined: Sep 14, 2004
    Posts: 4,449

    57JoeFoMoPar
    Member


    Not at all. Maybe it's just because I do so much machine work, but .030 is a fairly substancial amount of metal. Think about this for a moment. The driveshaft is .030 out at one end. Though the small amount that the .030 weighs may seem miniscule, once you apply the rotation of 3000+ rpm, suddenly that negligible weight maybe be 10 or more lbs. Think about how a 10 lb barbell strapped to a straight driveshaft would feel. That murder on your transmission, not mention makes it prone to breaking.

    I've seen driveshafts come apart and its not pretty. $200 for a perfect new driveshaft is cheap insurance for myself, my car and anyone that rides with me
     
  19. OldSub
    Joined: Aug 27, 2003
    Posts: 1,064

    OldSub
    Member Emeritus

    I've done it...

    Used a lathe to cut the shaft and clean things up. Had a certified welder do the welding for me. It was the front of a 4x4 and it ran fine for several years before I sold it.

    Being 25 years older I'd rather pay aro now...
     
  20. brandon
    Joined: Jul 19, 2002
    Posts: 6,324

    brandon
    Member

    use a large pipe cutter .....and have the yoke weld trimmed in a lathe......its pretty simple....brandon
     
  21. spellsinger
    Joined: Mar 10, 2006
    Posts: 30

    spellsinger
    Member
    from California

    Just a note to find a square cut on a tube. Use a plumbers tubing cutter. The rollers will keep it square, and make a perfect line to cut. All the best:
    tom
     
  22. I've done a few, Kermit has one in his car, but he doesn't know it's mine...

    Cutting the shaft is NOT critical, close is more than good enough.
    Care in removing the yoke(s) is more important.
    To clock the yokes, I've always used a smooth, concrete floor, rocking until there is no rock.
    I also use a dial indicator. With the shaft in place (because I always have the trans and rear located before I do the shaft), I set it with the indicator, then attach a big 'C' clamp to the shaft, for the ground cable. Rotating the shaft with the rear wheel, tack it in four places, recheck, then finish weld. Wrapping the ground cable to unwind when welding works better.
    Reason for the 'C' clamp is to NOT run weld current through 'U' joints, BAD idea, that.
    If there is a balance weight, I cut the other end, or weld the weight back in the exact spot.
    No problems with any of my shafts, but I have never run ludicrous amounts of horsepressure through them, either (300 hp, max).

    I do auto tranmissions, too.

    Cosmo
     
  23. hotrodsigns
    Joined: Mar 6, 2006
    Posts: 13

    hotrodsigns
    BANNED

    I don't think there is any good way to get one to run true without a lathe. I run a machine shop and get $35 to shorten one. That's cheap if you think about what might happen if it isn't right. For what its worth be safe.
    ww.hotrodsigns.com
     
  24. hotrodsigns
    Joined: Mar 6, 2006
    Posts: 13

    hotrodsigns
    BANNED

    I don't think there is any good way to get one to run true without a lathe. I run a machine shop and get $35 to shorten one. That's cheap if you think about what might happen if it isn't right. For what its worth be safe.
    www.hotrodsigns.com
     
  25. Hip
    Joined: Jan 3, 2003
    Posts: 848

    Hip
    Member

    I did it on my 53 chevy panel useing only a big pipe cutter, two pieces of 2x2 angle iron, two big clamps, and a arc welder. I drew 4 perfectly straight lines down the shaft where it would be cut equal spacing around the diameter, (this is the key to keep yourself balanced). Obviously using the angle down the shaft will be a perfect line, so then you just decide how much is going and use the pipe cutter to twist that chunk off, and then chamfer the diameters edge just a little for penatration. Line your marks back up. (oh yeah, be sure to give one of the marks a definat refrence mark so you are lineing it back up with the right mark.
    Now use your angles again to line the shaft up perfectly to your marks and clamp them down. There is no way that the drive shaft will be off pinched tightly between two angles, and if your still paranoid you can use a second set of angles and clamps but you'll have to adjust a little to make your tacks. Which brings us to the last step welding it. On either side of the angle do a quick spot weld just to hold it together, and then what i did was pull off the clamps and have a buddy slowly rottisary it with an angle clamped in a big vise (just for something to hold the one end while he rotated and i welded.
    Couple hints...... I had a very small gap between the shafts !/16" just for even penetration and you want to make one pass only so that the weight even in the weld is as evenly distributed as possable. One more tip. Even if it looks ugly as long as you have good penetration- DON"T GRIND IT DOWN!!!- Maybe just to knock off the snagging welds but just the tops!
    Like i said i did this on the panel (that made at least one trip a month 3.5 hours to San Diego to see the folks) , NO VIBRATION. I also did it on my '66 Chevelle that i always was cautious about getting into the throttle because i did the shaft but it to never gave me problems. IT CAN BE DONE AT HOME.
    DocFranknsteins done quite a few too!
     
  26. Model40-770
    Joined: Aug 24, 2005
    Posts: 273

    Model40-770
    Member
    from LOUISIANA

    i have helped with one......we used a tubeing cutter to cut the shaft and took our time cutting the end off the rest of the shaft and fitting it to the shortened shaft........and i have one in my shop someone made i got out of a old project.......they used two transmission yolks and a piece of pipe.......don't know how good it worked but it was only a little over ft long........
     

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