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  1. #1
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    Default 2005 GXP Rear Thumping

    Sorry if this has been covered already, but didn't really see what I was looking for in previous posts. My 05 GXP has terrible thumping noise in rear, so I assumed it was the struts and/or mounts. I have Bilsteins. When I took it apart it looked as though the mount was fine, but can't really tell whether the strut is shot. I'm just wondering if maybe the top nut came loose on each side?

  2. #2
    GTP Level Member LeadfootCJ7's Avatar
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    Default Re: 2005 GXP Rear Thumping

    When does it do it? Over bumps, going down rough roads, smooth roads, on takeoff, all the time?
    2007 Grand Prix GXP;2002 Camaro Z28 - tune, CAI, and exhaust
    2006 GMC 2500HD - ATS high flow manifolds and uppipes, turbo back exhaust, blocked EGR, Denali headlights, Reflexxion Cown Hood
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  3. #3
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    Default Re: 2005 GXP Rear Thumping

    Pretty much when going over bumps and rough road, and taking off also.

  4. #4
    GT Level Member mguzzo's Avatar
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    Default Re: 2005 GXP Rear Thumping

    exhaust hitting anywhere underneath?
    --
    Current '98 GTP Coupe: Still stock and rust free. That will change.
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  5. #5
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    Default Re: 2005 GXP Rear Thumping

    I just put new exhaust on, but did not see anywhere it could be hitting

  6. #6
    GTP Level Member buickman104's Avatar
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    Default Re: 2005 GXP Rear Thumping

    Strut mounts? Pop off any covers over the rear strut mounts in the trunk and bounce the rear susppension and look for cracks in the rubber strut mounts.

    Also check the rear sway bar bushings. When worn they with make the car make noise over bumps.
    2000 Bronze Metallic GTP
    Power :Gen V, 3.6 pulley, 3 inch down pipe, Power log, FWI,and DHP Power Tuner,
    Handling: Vogtland Springs, GMPP sway bars, STBS, 18" Konig backbone, CTS-V Front brakes and GXP rear brakes

  7. #7
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    Default Re: 2005 GXP Rear Thumping

    Quote Originally Posted by buickman104 View Post
    Strut mounts? Pop off any covers over the rear strut mounts in the trunk and bounce the rear susppension and look for cracks in the rubber strut mounts.

    Also check the rear sway bar bushings. When worn they with make the car make noise over bumps.
    The strut mounts looks good, looks like there's a little play between dust cover and strut mount. Haven't checked the bushings yet.

  8. #8
    GrandPrix Junkie
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    Default Re: 2005 GXP Rear Thumping

    How does the tread wear look on the rear tires? Any signs of cupping? If so, then the struts are shot and letting the tires bounce/skip over bumps, creating the uneven wear patterns in the tread.

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    Default Re: 2005 GXP Rear Thumping

    Check the little trailing arm that sets rear toe. Mine made noise for a while and finally got under there and the nut on one side was loose and causes it to clunk when going over bumps.
    An engine is an engine no matter the size.... I think Dr. Seuss said that... or maybe it was Big Weld....

  10. #10
    GrandPrix Junkie spazzz's Avatar
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    Default Re: 2005 GXP Rear Thumping

    How many miles on struts?

    Tear the rubber off the strut mount in the trunk and check the nut. Chances are they are fine and you have to go strut shopping.

    That is the exact noise I had on rear FE3s with 20,000 on them

  11. #11
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    Default Re: 2005 GXP Rear Thumping

    Quote Originally Posted by spazzz View Post
    How many miles on struts?

    Tear the rubber off the strut mount in the trunk and check the nut. Chances are they are fine and you have to go strut shopping.

    That is the exact noise I had on rear FE3s with 20,000 on them
    Car has 85,000 on it. Only had it a year and a half, so not sure when they were last changed. Did the Bilsteins only come with the FE4, or were they offered on other packages? Still can't tell all of these apart...

  12. #12
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    Default Re: 2005 GXP Rear Thumping

    I had local shop check out my strut, they said it is fine. The old strut mount looks beefier than the new Monroe mount I bought. So I guess I'm looking into the sway bars and ends.

  13. #13
    GrandPrix Junkie spazzz's Avatar
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    Default Re: 2005 GXP Rear Thumping

    Bilsteins only came on the GXP.
    I replaced everything back there except the forward lateral.

    The struts were my clunk/thump.

    If and when you get it figured out, post back.

    Your yellow Bilsteins are no doubt original at that many miles

  14. #14
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    Default Re: 2005 GXP Rear Thumping

    Looks like it was my rear sway links. Got some new ones, and sound is gone.

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