Page 1 of 3 123 LastLast
Results 1 to 20 of 51

Thread: Don't box your L body subframe, here's why.

  1. #1
    turbo addict
    Join Date
    Dec 2005
    Location
    Mesa, AZ
    Posts
    6,747

    Don't box your L body subframe, here's why.

    I had a two inch sheet metal welded to my GLH's body rear subframe's U channel. At first, the rear suspension was really stiff, it would lift the rear wheel when there is a slight incline on the parking lot I drive into. Then, I felt the rear suspension get softer and softer as it no longer lift the rear wheel as much anymore. Maybe a year later since I welded the subframe, I noticed the cracks.

    I now uses a n/a omni subframe with a polybushing sway bar.
    http://polybushings.com/pages/swaybarLrr.html

    My advise don't box up the U channel or you'll be needing to replace it soon.


















  2. #2
    turbo addict
    Join Date
    Dec 2005
    Location
    Spokane, Wa
    Posts
    8,820

    Re: Don't box your L body subframe, here's why.

    LOL. What size PB rear sway bar did you end up with? I put the 1 1/8" on my GLHT and cut the stock bar off. Under 30mph stuff was a lot of fun. Over 30 MPH was dangerous oversteer. It snapped around on my entering a freeway off-ramp when I had to nail the brakes to not hit the car in front who decided to take it 20MPH slower than needed. Thankfully I had the skills to catch it and keep from hitting the light pole.

  3. #3
    Hybrid booster
    Join Date
    Dec 2005
    Location
    Flemington, NJ
    Posts
    438

    Re: Don't box your L body subframe, here's why.

    Quote Originally Posted by GLHNSLHT2 View Post
    LOL. What size PB rear sway bar did you end up with? I put the 1 1/8" on my GLHT and cut the stock bar off. Under 30mph stuff was a lot of fun. Over 30 MPH was dangerous oversteer. It snapped around on my entering a freeway off-ramp when I had to nail the brakes to not hit the car in front who decided to take it 20MPH slower than needed. Thankfully I had the skills to catch it and keep from hitting the light pole.
    Brake bias issue?

  4. #4
    Supporting Member II Turbo Mopar Contributor ajakeski's Avatar
    Join Date
    Sep 2007
    Location
    SE Wisconsin
    Posts
    2,312

    Re: Don't box your L body subframe, here's why.

    It has to bend somewhere.
    I used a 7/8 inch ADDCO bar mounted over the stock welded on bar. It made for a very neutral handling car, but when compared to driving my other GLH with only the stock bar, I didn't notice much difference. Both handled similarly and produced identical autocross times. Both cars cornered on three wheels.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	IMG_9794.jpg 
Views:	155 
Size:	680.5 KB 
ID:	57445  
    http://www.greatlakeshotrod.com/Grea...kage_Kits.html
    L-Body Shift Linkage Upgrade all in one convenient kit!

  5. #5
    Moderator Turbo Mopar Staff Vigo's Avatar
    Join Date
    Feb 2006
    Location
    San Antonio,TX
    Posts
    10,725

    Re: Don't box your L body subframe, here's why.

    I haven't noticed any breakage on the k-car axles I've welded, other than the actual welds I added cracking.

    Dont push the red button.You hear me?

  6. #6
    Supporting Member II Turbo Mopar Contributor 83scamp's Avatar
    Join Date
    Mar 2013
    Location
    Columbia City, Indiana
    Posts
    1,079

    Re: Don't box your L body subframe, here's why.

    Quote Originally Posted by Vigo View Post
    I haven't noticed any breakage on the k-car axles I've welded, other than the actual welds I added cracking.
    Yeah, but the K-based rear axle is an entirely different animal than the L-body. The L-body was listed as a semi-independent rear suspension. You don't want to box the connecting member for exactly this reason. It HAS to flex. Box it in, and it will flex at the next weakest area, which is most likely where the cracks occured...

    It's a very good lesson, and I am glad tryingbe posted it as a good "this is what not to do" lesson for others...
    83 Scamp GT, 2.5 TII/A-520
    89 Dodge Daytona ES turbo, Daily driver

  7. #7
    Moderator Turbo Mopar Staff Vigo's Avatar
    Join Date
    Feb 2006
    Location
    San Antonio,TX
    Posts
    10,725

    Re: Don't box your L body subframe, here's why.

    Well, they're both torsion beams and 'semi' independent. I guess the k-car part was built with the benefit of L-body hindsight as it's simpler and more compact and apparently holds up better to the same basic modification. It looks like strengthening (or doubling up?!) the actual torsion bar going all the way across there would be safer as it puts its forces into the strongest-looking part of the whole thing.

    Dont push the red button.You hear me?

  8. #8
    Supporting Member II Turbo Mopar Contributor
    Join Date
    Dec 2005
    Location
    Sylmar, CA
    Posts
    2,403

    Re: Don't box your L body subframe, here's why.

    Years ago, I stitch welded a simple piece of strap onto the bottom of that U channel on the GLHT; within a short time that strap was banging and slapping as the twisting cracked several of those stich welds. After that, I installed Johnny's rear sway bar (without cutting out the stock torsion bar) which stiffened the car up a lot. I recently went back to stock for daily driving.
    John Laing

    "The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
    -- Alexis de Tocqueville

    "One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary."
    --Ayn Rand

    "To evolve, you don't need a Constitution. All you need is a legislature and a ballot box . . . . things will evolve as much as you want. All of these changes can come about democratically; you don't need a Constitution to do that and it's not the function of a Constitution to do that."
    -- Justice Antonin Scalia

  9. #9
    turbo addict
    Join Date
    Dec 2005
    Location
    Spokane, Wa
    Posts
    8,820

    Re: Don't box your L body subframe, here's why.

    Quote Originally Posted by DevoBuzz View Post
    Brake bias issue?
    not in a straight line, but with the inner rear wheel up off the ground and the outer rear riding the shoulder on 1" square contact patch probably. It had stock rear brakes and a SLH1 package on the front. Like I said, tons of fun at low speed as you could rotate the car way to easily. At high speed at neutral or negative throttle it was way worse than any 911 I've driven.

  10. #10
    turbo addict
    Join Date
    Dec 2005
    Location
    Mesa, AZ
    Posts
    6,747

    Re: Don't box your L body subframe, here's why.

    Quote Originally Posted by GLHNSLHT2 View Post
    What size PB rear sway bar did you end up with?
    1 inch. I have not experience any oversteer issue, not even when I drove it hard at autocross. I don't drive aggressively in the wet.

  11. #11
    Supporting Member II Turbo Mopar Contributor Shadow's Avatar
    Join Date
    Dec 2006
    Location
    Aubigny, Manitoba, Canada
    Posts
    4,875

    Re: Don't box your L body subframe, here's why.

    That U channel was obviously meant to flex, def do Not want to be welding that up!

    When I hole drilled the Charger rear member (some may remember certain people having heart attacks over this LMAO!!!) I Knew all I was doing, along with removing weight, was making for an Easier flexing rear suspension. Since I also knew I was adding the 1" PB rear sway bar, this was of no concern to me.

    Now, was it shear Luck that I ended up with the most well balanced rear suspension I could have ever hoped for................

    Robert Mclellan
    http://www.youtube.com/watch?v=wambNdfnu5M
    10.04 @ 143.28mph (144.82 highest mph)
    Worlds fastest 8v MTX Shelby Charger
    Manitoba's Fastest 4cyl!
    8 valve, No Nitrous!
    New clutch combo is the SH!T!

  12. #12
    Supporting Member Turbo Mopar Contributor supercrackerbox's Avatar
    Join Date
    Dec 2005
    Location
    Firth, Nebraska
    Posts
    4,786

    Re: Don't box your L body subframe, here's why.

    Now I'm curious how to approach my GLHS. The front bar is a shortened 1.25" Daytona unit with heim joint end links. This has been done and sitting on the shelf for years waiting for the car to be done. My rear axle is sitting with a pile of other parts waiting for powdercoating, but I need to decide on the rear bar before doing so. Stock bar by itself? Stock bar with the PB rear bar added? Cut off the stock bar and just run the PB bar? FWIW, the rest of the suspension will be rebuilt factory Konis with the LRE lowering springs and stock brakes.

    Brakes may be upgraded in the future, but no plans for that yet.

  13. #13
    Supporting Member Turbo Mopar Contributor supercrackerbox's Avatar
    Join Date
    Dec 2005
    Location
    Firth, Nebraska
    Posts
    4,786

    Re: Don't box your L body subframe, here's why.

    On a side note, one of the first things I noticed about the new Fiesta ST is that their "twist beam" rear axle design is incredibly similar to our L-bodies, as was the GM J-body design from the '80s to early '90s. So there has to be some benefit to the design.

  14. #14
    turbo addict
    Join Date
    Dec 2005
    Location
    Mesa, AZ
    Posts
    6,747

    Re: Don't box your L body subframe, here's why.

    Quote Originally Posted by supercrackerbox View Post
    Now I'm curious how to approach my GLHS.

    1-1/8 inch poly bar with no stock sway bar.
    http://polybushings.com/pages/swaybarLrr.html

    Quote Originally Posted by supercrackerbox View Post
    So there has to be some benefit to the design.

    It's CHEAPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP!!!

    Look at the high cost FWD cars and see who uses this design.

  15. #15
    Supporting Member Turbo Mopar Contributor supercrackerbox's Avatar
    Join Date
    Dec 2005
    Location
    Firth, Nebraska
    Posts
    4,786

    Re: Don't box your L body subframe, here's why.

    Quote Originally Posted by tryingbe View Post
    It's CHEAPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPP!!!

    Look at the high cost FWD cars and see who uses this design.
    Fair point. But it seems to be an effective alternative to a true independent rear suspension.

  16. #16
    turbo addict
    Join Date
    Dec 2005
    Location
    Mesa, AZ
    Posts
    6,747

    Re: Don't box your L body subframe, here's why.

    Quote Originally Posted by supercrackerbox View Post
    Fair point. But it seems to be an effective alternative to a true independent rear suspension.
    I would argue it's just cheaper to make and assemble.

    Neon.


    Saturn S series.

  17. #17
    Moderator Turbo Mopar Staff Vigo's Avatar
    Join Date
    Feb 2006
    Location
    San Antonio,TX
    Posts
    10,725

    Re: Don't box your L body subframe, here's why.

    My Insights and Prius use a very similar design to the l-body piece. Ground clearance is definitely better with that vs the K-car type.

    Dont push the red button.You hear me?

  18. #18
    turbo addict
    Join Date
    Dec 2005
    Location
    Mesa, AZ
    Posts
    6,747

    Re: Don't box your L body subframe, here's why.

    Toyota Matrix



    Toyota Corolla


    Nissa Sentra

  19. #19
    Supporting Member II Turbo Mopar Contributor
    Join Date
    Dec 2005
    Location
    Sylmar, CA
    Posts
    2,403

    Re: Don't box your L body subframe, here's why.

    So, is there a consensus as to the best design for the rear suspension on a front wheel drive car?
    John Laing

    "The sole condition which is required in order to succeed in centralizing the supreme power in a democratic community, is to love equality, or to get men to believe you love it. Thus the science of despotism, which was once so complex is simplified, and reduced . . . . to a single principle."
    -- Alexis de Tocqueville

    "One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary."
    --Ayn Rand

    "To evolve, you don't need a Constitution. All you need is a legislature and a ballot box . . . . things will evolve as much as you want. All of these changes can come about democratically; you don't need a Constitution to do that and it's not the function of a Constitution to do that."
    -- Justice Antonin Scalia

  20. #20
    turbo addict
    Join Date
    Dec 2005
    Location
    Mesa, AZ
    Posts
    6,747

    Re: Don't box your L body subframe, here's why.

    Fully independent suspension would be my guess.

Page 1 of 3 123 LastLast

Similar Threads

  1. Daytona (G-Body) Subframe connectors
    By tommyturbo in forum Group Buys
    Replies: 36
    Last Post: 03-14-2016, 02:57 PM
  2. Subframe 1987 J body LeBaron
    By LeBaronMike in forum Suspension, Brakes, Wheels, Traction
    Replies: 5
    Last Post: 04-25-2013, 07:23 PM
  3. Rampage subframe
    By moparman1991 in forum Interior, Exterior and Chassis Modifications
    Replies: 8
    Last Post: 10-14-2012, 07:17 PM
  4. Subframe for RWD
    By AO_2JZ in forum Custom Turbo Mopars
    Replies: 3
    Last Post: 03-05-2009, 01:47 PM
  5. Subframe connectors
    By tommyturbo in forum Interior, Exterior and Chassis Modifications
    Replies: 79
    Last Post: 03-03-2009, 02:46 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •