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Need Help!!! Clunking, rattling, & grinding sound from rear end

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  • #1

    Need Help!!! Clunking, rattling, & grinding sound from rear end

    Well since this has finally gotten on my nerves enough I figured I would turn to the experts before I go taking the car into the shop to see what's wrong...here's the problem:

    I have a 98 Formula with 16" wheels on it. Last year I bought new chrome 18" Zenetti Vega wheels and new low profile tires and put them on. Ever since then whenever I go over bumps and lumps in the road I get this clunk/rattle from the rear end. I figured, ok rougher ride from the new wheels, no big deal. Then comes the more terrifying part. If I goto take off from a stop, going around a corner, while the wheels are trying to get grip on the road this horrible grinding noise comes from the rear end till the wheels gain grip. I've also tried to do a couple brake stands in it's lifetime with no problem with the old wheels, but get the horrible grind with the new ones again.

    I don't really have anything else to go on as this has only started since the new wheels. Does anybody have any idea what the problem might be? Or am I doomed to take it into the shop and hopefully they can figure something out.

    As an add on to this I bought some jounce bumper spacers on the suggestion of somebody else and that didn't fix the problem. However when I took the wheels off I noticed no evidence of rubbing, however there was something that looked out of the ordinary. I don't know what the piece is called but it was bent on both sides. I don't have a digital camera but drew a bad sketch of it. Here's what it looked like:



    Can anybody tell me if that's normal or whether or not that might be causing the sound I'm hearing? And can it be fixed?
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  • #2
    That looks like your rear sway bar. Its sopposed to be bent in a kind of a U shape (looking from the top). The middle of the bar bolts on the the axle by two clamps and bushings. The ends are fastened to a couple of bolts (One per side) and fastened to the frame. Look at the bushings that that go on each side of the sway bar link hole. They should not be deformed or loose enough to cause any end play in the bar.
    LT4KM, 160 degree TS, MAF ends, TB-bypass
    1.6 Roller Rockers, SLP CAI, LCA, tierod, 17x9" Wheels F/R, 275/40R17 Goodyear F1 tires.
    WS6 Muffler, LS1 Alum. Drive shaft. 21mm rear sway bar
    Soon to be LT4 heads, intake, & HOT cam

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    • #3
      Also on the end of the sway bar that links to the frame bracket there is a long bolt going though a tube spacer, bushings and washers to fasten all this together. 1 tube spacer, 4 bushings and 4 washers per side. If memory serves.
      LT4KM, 160 degree TS, MAF ends, TB-bypass
      1.6 Roller Rockers, SLP CAI, LCA, tierod, 17x9" Wheels F/R, 275/40R17 Goodyear F1 tires.
      WS6 Muffler, LS1 Alum. Drive shaft. 21mm rear sway bar
      Soon to be LT4 heads, intake, & HOT cam

      Comment

      • #4
        Yea the problem is where the arrow is pointing that says (this is bent), there is some space between the piece and the two bushings on either side. I think the picture is probably bad. Where the piece attaches to the axel, there is a u-bolt over the axel and then it is attached below the axel to that bushing that is hold on by the u-bolt. There is also a long straight bar that isn't in the picture that is bolted above that that goes from one side to the other along the axel, but one side was higher than the other (it could be because I had the one side jacked up at a time).

        So I'm wondering if the noise I am getting is from that space and what I can do to correct it. And would the new 18" wheels cause that problem in the first place.

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        • #5
          There is a diagonal bar that runs from the back of the drivers side of the axle housing, to the body on the passenger side. That is the "panhard bar" and that is supposed to be angled. You can see the passenger end of it in the pic below:



          Right above that, there will be another diagonal bar, from the passenger side of the body where the panhard rod attaches, to a point higher on the drivers side of the body. Both the panhard rod and the brace are u-shaped (in stock form) sheet metal stampings. Replacing the panhard rod with a more ridgid tubular bar is a popular mod for improved handling. It positions the body side-to-side over the rear axle.

          As far as the sway bar, it should be attached to the axle via the bushings, and those should be directly under the axle, not tilted forward or backward. You can see them in the photo above. The "ends" of the sway bar are connected to the body by "end links".... long, straight bolts with bushings on top and bottom. If that end link is bent, it could be causing the sway bar to pre-load the suspension and keep the back of the car from sitting level.

          You can see the end link in this picture... and it is straight.



          Don't compare the exact shapes and colors of anything in those pic's to a "stock" setup, because very few of the items in those pic's are "stock".... just trying to show you where things are located
          Fred

          381ci all-forged stroker - 10.8:1 - CNC LT4 heads/intake - CC solid roller - MoTeC engine management - 8 LS1 coils - 58mm TB - 78# injectors - 300-shot dry nitrous - TH400 - Gear Vendor O/D - Strange 12-bolt - 4.11's - AS&M headers - duals - Corbeau seat - AutoMeter gauges - roll bar - Spohn suspension - QA1 shocks - a few other odds 'n ends. 800HP/800lb-ft at the flywheel, on a 300-shot. 11.5 @ 117MPH straight motor

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          • #6
            Great that was exactly one of the pictures I was looking for. I am gonna show you which part is bent and where there are gaps on either side of this piece. The part is circled in red.



            Would that part being bent with gaps on either side be causing the rattling?

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            • #7
              Those are your endlinks. I have no idea how they got so bent up - maybe your car is bottoming out too much - Did you cut coils off your springs or lower the car somehow?

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              • #8
                If your swaybar end links are broken that would deffinetly cause a rattling (Intermitten contact between bar and end link) and that side to move in suspension travel too much. If the bar is undamaged you should just replace the bolt and spacer and maybe the bushings and washers are still good.
                LT4KM, 160 degree TS, MAF ends, TB-bypass
                1.6 Roller Rockers, SLP CAI, LCA, tierod, 17x9" Wheels F/R, 275/40R17 Goodyear F1 tires.
                WS6 Muffler, LS1 Alum. Drive shaft. 21mm rear sway bar
                Soon to be LT4 heads, intake, & HOT cam

                Comment

                • #9
                  I say bent but it wasn't and extreme bend in the end of it...just enough for me to notice it...and since I've heard the rattle come out of both sides, I figured it would look the same on both and it did...so it is probably the gap on both sides of it that is causing the rattle

                  I haven't done any kind of work on the suspension at all...the only thing I did was put on 18" wheels in place of the stock 16" ones I had on it...so maybe that did something to it...

                  I think I'm gonna give a shop a call around here as I am far from qualified to do the work myself...plus I don't have the place or tools to do the job...which is what sucks living in an apt. building...

                  If anybody else has any opinions I'm open to 'em, otherwise I guess I'm just see if I can get that piece fixed and hope the sound goes away...

                  Comment

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