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Chassis Stiffening Ideas?

Discussion in 'Intermediate CJ-5/6/7/8' started by Iandavidh, May 7, 2020.

  1. May 7, 2020
    Iandavidh

    Iandavidh Member

    California
    Joined:
    Sep 24, 2018
    Messages:
    398
    What are everyone’s solutions for stiffening up the chassis on our old cjs? Is it worth it?

    I figure the easiest way would be to tie the cage into the frame at the front hoop and the rear kickers. Does this create issues with just the front 1/3 or so of the frame taking flex because it won’t be connected? That part is already boxed from the factory.

    The other way would be to take the body alllll the way off and completely box the frame. I’ve seen people boxing only certain high stress areas on the frame what about that?

    The Jeep just doesn’t seem too solid when driving it on the road. You can feel the movement of the frame and body even after new poly bushings and suspension. It’s adequate enough and I know it’s kind of a the way of the road with these things but I would like to make improvements and hear everyone’s opinion.
     
  2. May 7, 2020
    wheelsontheroof

    wheelsontheroof New Member

    dupont pa
    Joined:
    Apr 1, 2020
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    37
    most jeeps dont have sway bars like modern vehicles. combine that with short wheelbase and high center of gravity . I dont know what a completely rigid frame would do to improve that. I used a 77 cj5 as a daily driver for 10 years and always had to concentrate on driving. what do you need it to do as far as how fast you like to drive or handling.
     
  3. May 7, 2020
    Iandavidh

    Iandavidh Member

    California
    Joined:
    Sep 24, 2018
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    398
    I am pretty satisfied with the handling like it is but on rough roads it is a little much. I definitely need a new steering stabilizer and wider tires and wheels. My main concern is the feeling of disconnect between the frame and the body. I only go 50 around town and 60-65 on the freeway
     
  4. May 7, 2020
    wheelsontheroof

    wheelsontheroof New Member

    dupont pa
    Joined:
    Apr 1, 2020
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    37
    in the old days we would make new body mounts out of hockey pucks. some guys stacked them for body lift. handling does start to deteriorate above 45. the rough offroad ride comes with leaf springs. with bigger tires they are sensitive to tire pressure. with 33 / 12.50 tires I could run 12 psi in the rear tires around town and 20 in the fronts. not good for highway
     
  5. May 7, 2020
    wheelsontheroof

    wheelsontheroof New Member

    dupont pa
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    Apr 1, 2020
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    what condition are tub body mounts . the sheet metal.
     
  6. May 7, 2020
    Iandavidh

    Iandavidh Member

    California
    Joined:
    Sep 24, 2018
    Messages:
    398
    solid except for the passenger front hat channel under the floorboard and the passenger rear body mount. Those definitely need to be fixed and will make a little difference but I feel like it will still leave a little to be desired. I have also done a little bracing at the very front hat channels on both sides.
     
  7. May 7, 2020
    wheelsontheroof

    wheelsontheroof New Member

    dupont pa
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    Apr 1, 2020
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    the rear body mounts bad will make it feel like its falling apart. no weight on the back end equals maximum bounce
     
  8. May 8, 2020
    Sierra Bum

    Sierra Bum Member

    The High Sierra
    Joined:
    Oct 23, 2017
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    329
    I think one of the best ways to stiffen and support the frame on these old Jeeps is to weld in front and rear crossmembers between the frame horns where the bolt-in bumpers are...or something similar. 3/16” 2x4 tubing works well. Then I’m also a fan of boxing and strapping because you’ll transfer the stress points.

    I experienced a frame failure years ago half way through the Rubicon Trail. That made me think twice about the weakest link.

    As with any mod, one leads to another. A stiffer, stronger frame needs a well thought out suspension. Let a nice set of springs do the flexing....that’s my philosophy.
     
    wheelsontheroof likes this.
  9. May 8, 2020
    Iandavidh

    Iandavidh Member

    California
    Joined:
    Sep 24, 2018
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    398
    The intermediates came from factory with those crossmembers. What specific areas would you box? The whole thing or parts?

    Exactly mine as well:). I’ve got BDS springs under there so I think I’m pretty set there
     
  10. May 8, 2020
    Sierra Bum

    Sierra Bum Member

    The High Sierra
    Joined:
    Oct 23, 2017
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    329
    The intermediates like the ecj5s have crossmembers (bumpers) yes, but I’m pretty sure they are only bolted in...and bolts alone allow movement. I’ve welded and gusseted in 3/16 2x4 tubing inside and between the frame horns on a couple rigs and it seems to limit the frame moment quite a bit. A nice set of bumpers can be fabbed up to do this too of course.

    The early jeeps were probably designed to have frames that move with the Jeep, but 50+ years of that takes a toll on a steel chassis.

    For me, if I was starting fresh, I’d box the entire frame and strap the spring hanger and shackle bracket areas. My current Jeep has welded, gusseted bumpers into the frame and the frame is boxed and strapped in other common trouble/stress areas...and I’m not pulling the body off any time soon to do more. It does have a pretty flexible suspension.

    Like so many of our projects there is a practical side. Time, money, resources, work space. I’d love to just throw my classic stuff on a custom frame with a sweet suspension and go Jeeping...no worries. I suppose we have to decide what our goals are and what is possible with what we’ve got to work with.
     
  11. May 8, 2020
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
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    23,596
    Crawling around under my Jeep, everything is riveted together, but there are selected welds to supplement the rivets.

    I kinda don't want to get involved in this - Search old posts. Plenty of discussion of the various trade-offs. Bottom line is you can't have it all with this suspension design - you have to compromise somewhere.

    When I was hanging around at Chuchua's, they prepared one of the new Renegades in 1972 for a couple of journalists to run one of the Baja races as publicity. Frame reinforcement consisted of welded blocks to prevent front shackle inversion and bent front spring leaves, and strapping on the top and bottom frame rails. I would be reluctant to do any additional boxing.
     
  12. May 8, 2020
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
    Joined:
    Aug 13, 2015
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    One thing I’ve learned from beating on these things for a better part of my life... either do nothing at all or do everything.

    The original design is built to flex, and if you notice the problem spots? The few spots that were welded or reinforced and not allowed to flex with the rest of the frame. The spring hangers, around the crossmember under the radiator, and around the crossmember under the center of the bed. If any boxing or stiffening is done, box the entire frame.

    This also applies to cage work. If the cage, or the points where the cage mounts to the frame are too stiff, the frame will develop cracks in the frame around the front hoop’s mounts in particular. The cage will hold the rear half of the frame from flexing as much as the front. This can be helped with (a) a rubber/nylon bushing-mounted cage, (b) a cage that continues through the engine compartment to the front bumper, or (c) a thoroughly boxed frame that won’t transfer flex to the cage mounts.
     
  13. May 8, 2020
    wheelsontheroof

    wheelsontheroof New Member

    dupont pa
    Joined:
    Apr 1, 2020
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    even something like a fish plate is more complicated than it looks . I was around guys who fixed frames on big stuff . real artists
     
  14. May 11, 2020
    BadGoat

    BadGoat How High Can You Climb?

    Northern Virginia
    Joined:
    Apr 27, 2017
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    Be careful when reinforcing the frame that you don't create stress risers around the reinforcements. I cheated and went with a new box tube frame from Throttle Body Kustoms. I don't have any problems with it flexing.

     
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