1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Rear Driveshaft Length?

Discussion in 'Early CJ-5 and CJ-6 Tech' started by Buildflycrash, Sep 9, 2019.

  1. Sep 9, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955
    I only have about 1/4" of in travel on the stock driveshaft. It's causing trouble, damage to the rear pinion seal. I'm sure the TC isn't happy either.

    How much "IN travel" should I have? RR YJ spring conversion.

    Thanks
     
  2. Sep 9, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    9,079
    Obviously bottoming out on spring compression is your biggest concern. Sounds like your driveshaft isn't the stock one. I guess you could start with jacking the back end up and measuring how much spline shows from axle sag. Driveshaft shop near your area?
     
  3. Sep 9, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955
    There is a shop nearby. I just need to know how much I need to have it shortened? only has about 1/4'' of travel now.
     
  4. Sep 9, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    9,079
    That's what I'm getting at, you might have to determine it on your own. Or trailer it to the shop and see what they say?
     
  5. Sep 9, 2019
    kenb

    kenb Member

    Detroit
    Joined:
    Jan 22, 2019
    Messages:
    143
    I would guess a drive shaft shop could tell you what the standard is for free play. For mine I did some triangle math to prove it wouldn't bottom out even if the axle went all the way to the bump stops.
     
  6. Sep 9, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955
    Anyone have an "about ___inches" ?

    Algebra isn't going to happen no less geometry.
     
  7. Sep 9, 2019
    kenb

    kenb Member

    Detroit
    Joined:
    Jan 22, 2019
    Messages:
    143
    I think my stock setup is in the neighborhood of an inch to an inch and a half. I can check later in the week if nobody else chimes in.
    Edit- I found some old notes. I have a bit more than an inch.
     
    Buildflycrash likes this.
  8. Sep 9, 2019
    47v6

    47v6 junk wrecker! Sponsor

    Washington DC.
    Joined:
    Oct 25, 2006
    Messages:
    4,524
    Jack it up from the frame and see how it looks, then put it down and fill the back with weight until you bottom out. Divide
     
  9. Sep 9, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955

    They said there would be no Math!!
     
  10. Sep 9, 2019
    scott milliner

    scott milliner Master Fabricator

    Seattle Wa.
    Joined:
    Dec 17, 2002
    Messages:
    2,005
    Drive shaft shops only need, (wheels on the ground.) center of u joint to center of u joint. If you give them give them this info and your drive shaft. They can tell you if it is the right length.

    If you did a YJ lift. Your drive line length should get longer. As for your seal problem. Drive line length won't cause pinion seal damage.
     
    Last edited: Sep 9, 2019
    Buildflycrash likes this.
  11. Sep 9, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955

    Ok good. I’m learning as we go here. Really surprised that when I just pulled the shaft the total travel is only about 1 1/8”.
     
  12. Sep 9, 2019
    Glenn

    Glenn Kinda grumpy old man Staff Member Sponsor

    Apopka, Fl
    Joined:
    Sep 21, 2002
    Messages:
    9,079
    He only has a 1/4" play, so he'll have to disconnect the driveshaft for that. If it's already disconnected that's better yet and simpler.
     
  13. Sep 9, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955
  14. Sep 9, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955
    Does this look like an original drive shaft?

    Is 1 1/8” travel normal?
     
  15. Sep 9, 2019
    scott milliner

    scott milliner Master Fabricator

    Seattle Wa.
    Joined:
    Dec 17, 2002
    Messages:
    2,005
    Hard to tell. If it was professionally done, you couldn't tell.
     
  16. Sep 9, 2019
    kenb

    kenb Member

    Detroit
    Joined:
    Jan 22, 2019
    Messages:
    143
    I have a spare original at home. I can take some measurements and photos Wednesday if you need.
     
  17. Sep 9, 2019
    Twin2

    Twin2 wasn't me Sponsor 2019 Sponsor

    Virginia Beach, VA
    Joined:
    Apr 28, 2011
    Messages:
    3,804
    a good drive shaft shop . will calculate what slip needs to be built in . with vehicle flat on ground
    give the center of front u joint to center of rear u joint
     
  18. Sep 9, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955
    I pulled the shaft from the donor cj7 in the driveway. It has 2 3/4” travel. It would need to be cut lots more but I don’t think that will be a problem.

    [​IMG]
     
  19. Sep 9, 2019
    Norcal69

    Norcal69 Resident Taco Maker 2019 Sponsor

    Cottonwood, Ca
    Joined:
    Sep 6, 2014
    Messages:
    1,145
    You will be surprised just how little travel you actually need. As the rear suspension compresses, the rearend moves backwards, negating some of the shortening caused by the upward travel. 1/4" however is probably a cutting it a little close. If You are going to change your transmission in the near future, I would leave it alone for now as you will have to shorten the drive shaft when a 4 speed is installed.
     
  20. Sep 10, 2019
    Buildflycrash

    Buildflycrash Member Sponsor

    Gulf Breeze FL...
    Joined:
    Jun 5, 2007
    Messages:
    955
    Good point.
     

Share This Page

New Posts