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  1. #1

    Default Rebuild or buy a new control arm kit

    I’m starting to get some clunking in the rear end of my 85 fox body. It appears the upper and lower control arm bushings are worn out. I was thinking of just rebuilding the existing arms with new polyurethane bushings; however, that seems very labor-intensive and I was thinking of some of the kits offered on LMR. Has anyone had any good results with the kits. The J&M kit appears to be reasonably priced.
    thanks, Carey

  2. #2

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    Buy stock replacement uppers with rubber bushings and install new rubber bushings in the axle housing.

    Buy good lowers with the 3 piece poly ball bushings and you'll be set.

    DO NOT install poly bushings in the uppers!
    Jeremiah

    1986 Mustang GT 5spd, 3.27's
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  3. #3

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    286 has a good idea MM makes a nice lower have thought of doing that my self
    LIFE IS ONE LONG WEEKEND

  4. #4
    FEP Super Member webestang's Avatar
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    I advise to rent or buy this tool..... https://lmr.com/item/MM-MMT1/79-04-M...m-Bushing-Tool

    Scotty
    1985 Fox Notch 4-banger Ranger tube header Eastwood Royal Blue
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  5. #5

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    Thanks, good advice form all. I just ordered the maximum motorsports lowers, and the OEM uppers. Along with new differential mounts and coil spring Isolators. This should definitely quieting things up in the aft end. It was definitely the upper control arms. I mounted a go pro to the axle and the clunks were confirmed based on excessive play in the uppers.

  6. #6

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    I have a 4 inch long crack in my floor due to poly uppers, they dont allow the flex the rubber bushings do, I have since went to hyme joint style uppers with poly lowers.
    1979 Ford Mustang Pace Car
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  7. #7
    FEP Power Member qtrracer's Avatar
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    Quote Originally Posted by Shauncb View Post
    I have a 4 inch long crack in my floor due to poly uppers, they dont allow the flex the rubber bushings do, I have since went to hyme joint style uppers with poly lowers.
    Just to clarify why poly should not be used in the uppers. The upper arms are designed to perform two functions: lateral axle control and axle roll control. When the car goes into a turn, the uppers must lengthen through the rubber bushings and twist as well. Rubber and the channel designed upper allow this to occur until the bushings can no longer twist (they don't rotate in the sleeve) acting like a torsion spring. Poly prevents this from occurring causing earlier than expected bind. Bind causes the wheel rate (combination of spring rate, sta-bar rate and bushing bind) to go to infinity causing immediate traction loss. Since this is in the rear, the result is called snap oversteer. Oversteer is very difficult to correct once initiated even for pro drivers. This is why most OEMs build in understeer so that the driver can compensate and correct.

    If the handling wasn't bad enough, since poly doesn't allow the twist and lengthening required of the arm, the upper torque box mounting point takes lot of load it wasn't designed to handle. Cracking and ripping floors are the common result. Hence the reinforced torque box kits on the market.

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