Clunk from rear over bumps question?
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2004-2007 Cadillac CTS-V General Discussion Discussion, Clunk from rear over bumps question? in Cadillac CTS-V Series Forum - 2004 - 2007; Anyone give me ideas on a "clunk" I get when going over rough road/minor bumps? The sound almost comes from ...
  1. #1
    PJGross is offline Cadillac Owners Fanatic
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    Clunk from rear over bumps question?

    Anyone give me ideas on a "clunk" I get when going over rough road/minor bumps?

    The sound almost comes from the trunk, but not localized more than that, like I have something loose in the spare tire well that rattles around after a bump. However, there is nothing in there or in the trunk.

    It sounds like sway bar end link type rattle. However, they appear to be in good shape. I was also thinking perhaps a blown shock?

    After fixing my problem with the driveshaft bouncing off the exhaust during bumps, now it seems this is the last suspension/drivetrain noise I have that is unusual (I have whining rear and parade clunk up the wazoo but I'm not counting those).

    Any places to look would be great input. I wasn't sure if the rear diff upper mount could be banging off the body causing this or not? I haven't crawled under to check it out.

    -PJ

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  3. #2
    rand49er's Avatar
    rand49er is offline Cadillac Owners 10000+ Posts
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    Re: Clunk from rear over bumps question?

    My theory (as in my GC kit) is that the nut holding the shock's piston rod actually lifts off a bit when the shocks are compressed (jounce), then slap back during rebound. This was the essence of what the Feffman Fix tried to correct with the Ground Control kits. I still have the clunk though I've applied the Feffman Fix, and I've been thinking I should tighten the nuts on the top of the rear shocks another quarter turn.

    Well, it's a theory, anyway.
    '05 CTS-V, Maggie, Kooks, Hotchkis, Ground Control, Corsa, B&M, DSS/Hendrix, Full 3M Clear Bra, Autovation, V Headrests, CTS Console, STS-V 55w Fogs, Black Vette FRCs, Specter Werkes, Katech LS9 Clutch, SS Brake Lines, Heavymetals U-Turn Fuel Line Eliminator, Momo Combat Evo Shift Knob, Wldwhl Clear Sidemarkers, Linea Corse LC855 Wheels or OEM wheels w/'06-'07 Center Caps, plus a couple more. 472 RWHP/411 RWTQ (Mustang Dyno).

  4. #3
    thebigjimsho's Avatar
    thebigjimsho is offline Cadillac Owners 10000+ Posts
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    Quote Originally Posted by rand49er
    My theory (as in my GC kit) is that the nut holding the shock's piston rod actually lifts off a bit when the shocks are compressed (jounce), then slap back during rebound. This was the essence of what the Feffman Fix tried to correct with the Ground Control kits. I still have the clunk though I've applied the Feffman Fix, and I've been thinking I should tighten the nuts on the top of the rear shocks another quarter turn.

    Well, it's a theory, anyway.
    Did you do two washers? Worked for me...


    -- We miss you, JD (Dirt_Cheap_Fleetwood)


  5. #4
    rand49er's Avatar
    rand49er is offline Cadillac Owners 10000+ Posts
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    Re: Clunk from rear over bumps question?

    Quote Originally Posted by thebigjimsho View Post
    Did you do two washers? Worked for me...
    Yes. Big-ass ones. Somebody later posted that he tightened the nut way up, and that made a significant improvement. I tightened them once, but need to do it again, I guess. Maybe put a third BAW in there for good measure.

    Say ... where'd PJ go?
    '05 CTS-V, Maggie, Kooks, Hotchkis, Ground Control, Corsa, B&M, DSS/Hendrix, Full 3M Clear Bra, Autovation, V Headrests, CTS Console, STS-V 55w Fogs, Black Vette FRCs, Specter Werkes, Katech LS9 Clutch, SS Brake Lines, Heavymetals U-Turn Fuel Line Eliminator, Momo Combat Evo Shift Knob, Wldwhl Clear Sidemarkers, Linea Corse LC855 Wheels or OEM wheels w/'06-'07 Center Caps, plus a couple more. 472 RWHP/411 RWTQ (Mustang Dyno).

  6. #5
    PJGross is offline Cadillac Owners Fanatic
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    Re: Clunk from rear over bumps question?

    Hey Randy.... just trying to keep up with our 10 month old (girl) and our oldest girl going into Kindergarten starting August 1st!

    Haven't done really anything to the V lately, but I did get an orbital and some M102 and M205 and have been working on swirlmark issues and oxidized headlights.

    So no other problem spots to check in the rear? I will fill the gap at the trans mount to make sure that isn't the cause, and then look into that shock mod you were talking about.

    Is this something the corvette upper shock mounts would address if that is the source of the clunk?

    I'd like to rule out any other little things, first, though.

    Thanks,
    PJ

  7. #6
    Jason Brady is offline Cadillac Owners Member
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    Hi guys, just reading these posts. I had my 02 dts converted to coil spring. Makes a loud thumping noise on any size bump as the wheel descends quickly (like a hole). Somebody temporarily fixed the noise and said it was a dampner. Do you know what this is? Sound like the back end is going to fall off.

  8. #7
    xbladr is offline Cadillac Owners Fanatic
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    Re: Clunk from rear over bumps question?

    Did the OP ever get this resolved? I am having the exact same issue

  9. #8
    xbladr is offline Cadillac Owners Fanatic
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    Re: Clunk from rear over bumps question?

    It was the rear links installed new ones took about 45 minutes and the clunk is gone.

  10. #9
    PJGross is offline Cadillac Owners Fanatic
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    Re: Clunk from rear over bumps question?

    I will look at replacing mine as soon as I get my maggie belt back on. Wierd that they don't look worn to me. In other cases it seemed like it was obvious but I'll give it a shot. Thanks for revisiting this!

    -PJ

  11. #10
    xbladr is offline Cadillac Owners Fanatic
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    Re: Clunk from rear over bumps question?

    Mine looked find too but I had replaced everything else so I was running out of ideas. Gave this a shot for 50ish bucks and an hour of time it was well worth it.

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