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  1. #1
    FEP Power Member Broncojunkie's Avatar
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    Default Rear suspension loose after upgrades

    I recently did some work to the wife's 88gt. I found a good used 8.8 with 3.73 gear. I checked everything out and replaced the fluid and outer bearings and seals. I also replaced the upper control arms with factory pieces that were boxed-in. Bushings appeared to be brand new. I used non-adjustable aftermarket lowers. I bought them 2nd hand but I don't believe they were ever used. Again, bushings looked new.

    Along with these upgrades, I put a new set of Vision wheels (draglite knock-offs) and a new set of Cooper Cobra tires. Wheels are 15x8. Tires are 235/60, iirc.

    After doing the work, the rear end now feels squirrelly...or loose. It seems to float around. Never had an issue before the work. I went back over everything... even double checked torque settings. I can't see anything obvious that could cause it. Initially, I tightened everything as it was unloaded. When I re-torqued, I loosened everything and tightened it back up with the rear tires loaded (weight on the tires).

    Am I missing anything here?
    Last edited by Broncojunkie; 08-18-2017 at 10:23 AM.

  2. #2
    Moderator wraithracing's Avatar
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    The way I do my suspension bolts is to tighten the bolts/nut just until they make contact with the brackets then back off a quarter turn so you know the bolt/nut is loose, but won't come off.

    Then I drive the car around the neighborhood at 30 MPH or so, making sure to go over all the bumps, ruts, dips, etc. so the suspension will cycle as many times as possible. Then I pull back into the driveway and if possible for the rear back the car up on drive on ramps to get enough clearance to tighten everything up again. Then I push down on the rear hatch or trunk a couple of times to settle the suspension before torquing everything back to specs. That seems to work pretty well for me.

    I would try that first and see how the car feels, if you still have the floating feeling then I would start looking at your rear suspension components.

    I personally don't recommend the upper control arms being boxed, tubular, or with poly bushings. The OEM suspension geometry works best with stock unmodified OEM control arms and GOOD rubber bushings. Maximum Motorsports explains the reasons why here. http://www.maximummotorsports.com/te...p_panhard.aspx
    ​Trey

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  3. #3

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    What are you doing for rear shocks and how many miles are on them?

  4. #4
    FEP Senior Member cb650's Avatar
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    going to follow this I just bought the vision wheels also. Going to run 255 coopers on mine. Was considered about hub spacing on them. Going to buy or make some.

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    FEP Member brianj's Avatar
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    I wonder if the boxed uppers are binding and then breaking loose? Kind of how a seized ball joint can make a car squirrely driving down the road.
    1983 Mustang G.T. No-option stripper- I like strippers.
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  6. #6
    Moderator wraithracing's Avatar
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    Quote Originally Posted by brianj View Post
    I wonder if the boxed uppers are binding and then breaking loose? Kind of how a seized ball joint can make a car squirrely driving down the road.
    Could definitely be part of the issue. I also have to ask what brand of lowers did you install and what type of bushings are in them?

    As BrianJ suggested, I would bet suspension bind is part of the issue here, but hard to say if that is all of it.
    ​Trey

    "I Don't build it hoping for your approval! I built it because it meets mine!"

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  7. #7
    FEP Power Member Broncojunkie's Avatar
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    Shocks are older Bilstein, I think. Very few miles on them, but the car sat for a long time. Felt fine on the road prior to the upgrades. It's not a drag setup. More for handling. I'm curious if what I'm feeling is just the difference in the tires.

    As for the control arms, not sure on brand of lowers. The uppers, which are boxed oem, aren't boxed completely in. Just a piece of steel welded in the middle 2/3 length. The ends are still open. It wouldn't take much to swap the old ones back in, but I'll try doing what Wraith suggested first. Oh... and bushings are all rubber... uppers and lowers.

    Also forgot to mention that I replaced the coil spring isolators, as the old ones were trashed.

  8. #8
    FEP Power Member Broncojunkie's Avatar
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    Quote Originally Posted by cb650 View Post
    going to follow this I just bought the vision wheels also. Going to run 255 coopers on mine. Was considered about hub spacing on them. Going to buy or make some.
    I really like the Vision wheels, but I didn't like the lug nuts I bought for them. I messaged vision and never got a reply. No help from the vendor, either. I just ordered another set I'm hoping will work better. I think I may eventual get another set of them for my 86 coupe.

  9. #9
    FEP Super Member erratic50's Avatar
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    Do you have a panhard or watts link or just control arms?

    The triangulate upper control arms tend to bind up under side load anyway. Adding stiffer bushings makes the problem 10x worse.

    What are you running for springs? GT rear springs are stupid stiff compared to the front. That's why the 93 Cobra runs the same rate as 4cyl LX springs instead.

    what do you have for sway bar in back? The front bar itself is generally too stiff relative to springs and shocks/struts on the later 4-eyed foxes and the 87-93 LX sport and GT. The rear is also too stiff in stock form.

    on the street the stock front and no rear sway bar in back is about perfect. The rear sway bar tends to add a lot of bind into the rear. Was it loaded in some way when you installed it? That can add even more bind

  10. #10
    FEP Power Member Saturn V's Avatar
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    Unless you hear some rattling from the back from suspension components not tightened, I don't think the problem is your suspension. Your tires don't sound like they are too wide, but I have learned over the years that sidewall stiffness can vary widely. I think it is related to the load rating of the tires. Temporarily try your previous old tires on the rear and see what happens.


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  11. #11

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    Quote Originally Posted by brianj View Post
    I wonder if the boxed uppers are binding and then breaking loose? Kind of how a seized ball joint can make a car squirrely driving down the road.
    This

    I bought my 88xr7 with completely blown shocks. A cat jumped on the back of the car and it scared the crap out of me because the car bounced so much. It also had bad brakes, and when i fixed the brakes, i went out to check them. Middle of no where and layed on the brakes at about 60mph. Car swerved right, felt completely unnatrual. When i say swerved right, i mean like i almost lost control and drove off the road and straightened it out on the gravel along the side.

    Unable to describe what happened, i took my dad for a ride. I was thinking maybe one wheel was locking up or something, causing the swerve. So i fully expected it to go right. It didnt, it went left, this time kuch more violent and actually put me into a ditch. I was able to drive out and it didn't look like i hurt anything so i drove home.

    After trying a bunch of stuff, and replacing things, i pulled the shocks off my 350k mile 86 cougar and swapped them out. Id say the 86 shocks were also shot, obviously old and rusted, no paint left on them. Ive personally put at least 60k miles on them since i bought the car

    When i got the 88 shocks off, there was zero resistance, like none at all in the shock travel. I put the whimpy but resistant 86 shocks on, and instantly the random swerving was fixed. The shocks were so blown that as the nose dove and un loaded the rear, the rear end maxed out. The upper arms actually pull against each other at an angle. If they move too far, one of the two flex and the rear moves one side forwards and the other out, this is how the suspension "binds" in a stock setup.

    By boxing in the uppers, it makes it so the rear can no longer flex as much as it travels, and then it almost pops out of place in one of the bushings, causing the unnatrual feeling swerve. My skid marks when i went i the ditch, my car did a 90º turn at 50mph or so in one car length without ths front wheels moving from straight
    2 1986 cougars (both 4 eyed and 5.0)
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  12. #12
    FEP Senior Member cb650's Avatar
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    Quote Originally Posted by Broncojunkie View Post
    I really like the Vision wheels, but I didn't like the lug nuts I bought for them. I messaged vision and never got a reply. No help from the vendor, either. I just ordered another set I'm hoping will work better. I think I may eventual get another set of them for my 86 coupe.
    I got cragar 27804B and will use a deep 3/4 socket on them

  13. #13
    FEP Super Member erratic50's Avatar
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    Cooper Cobras are known to perform very well on a stock foxbody. We put a pair on my son's 86 5.0L 5-speed daily and it digs in and goes unexpectedly well. It's still running the stock throttle body and headers but is running a VM1 SD computer and is turned up from a timing perspective. It's no slouch at all and those tires are great on it.

  14. #14
    FEP Power Member Broncojunkie's Avatar
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    Quote Originally Posted by erratic50 View Post
    Cooper Cobras are known to perform very well on a stock foxbody. We put a pair on my son's 86 5.0L 5-speed daily and it digs in and goes unexpectedly well. It's still running the stock throttle body and headers but is running a VM1 SD computer and is turned up from a timing perspective. It's no slouch at all and those tires are great on it.
    I bought a set for my pace car (rears only) and a full set for this 88 after talking to you about them a few months ago. As soon as I get this issue straightened out, I'll get to see how they do. Actually, I've been on the river a little over 3 weeks. A few days to go and then I'll get back to working on the cars.

  15. #15
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    What tire pressure are you running in the rear , and the front ?
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  16. #16
    FEP Super Member erratic50's Avatar
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    Good luck! Coopers are made in the USA which is a big plus in my book too.

    Their truck tires have been great on my MarkLT. Those were rated for 65K and I got over 70 and I don't drive nice. My LT is turned up and makes 365 HP and 405Lbs at the tire. I'm on my 2nd set on it now.

    I ran CS4's on my Mountaineer and Sebring. Also lasted longer than their rating. CS5's on my dad's Mountaineer have been great too.

  17. #17

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    I had cooper cobras 235/60's and 275/60's on ten holes. Loved em to death. I got about 60k out of the front and around 80k out of the rears. Rears rubbed a bit. Id go 275/50's next time, but a very good tire.
    2 1986 cougars (both 4 eyed and 5.0)
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  18. #18
    FEP Power Member Broncojunkie's Avatar
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    Quote Originally Posted by ashley roachclip View Post
    What tire pressure are you running in the rear , and the front ?
    The tire shop put them at 32# all around, I think. I didn't mess with the pressure any. I was just excited to check out the rear and new gears.

  19. #19
    FEP Power Member Broncojunkie's Avatar
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    Quote Originally Posted by ashley roachclip View Post
    What tire pressure are you running in the rear , and the front ?
    The tire shop put them at 32# all around, I think. I didn't mess with the pressure any. I was just excited to check out the rear and new gears.

  20. #20

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    [QUOTE=wraithracing;1855748]The way I do my suspension bolts is to tighten the bolts/nut just until they make contact with the brackets then back off a quarter turn so you know the bolt/nut is loose, but won't come off.

    Then I drive the car around the neighborhood at 30 MPH or so, making sure to go over all the bumps, ruts, dips, etc. so the suspension will cycle as many times as possible. Then I pull back into the driveway and if possible for the rear back the car up on drive on ramps to get enough clearance to tighten everything up again. Then I push down on the rear hatch or trunk a couple of times to settle the suspension before torquing everything back to specs. That seems to work pretty well for me.

    I would try that first and see how the car feels, if you still have the floating feeling then I would start looking at your rear suspension components.



    interesting exercise loose first then tighten floating it into alignment

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