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2004-2007 Cadillac CTS-V Performance Mods Discussion, Clunk in Cadillac CTS-V Series Forum - 2004 - 2007; Could somebody point me to the thread where I could read about the clunk in the rear end or tell ...
  1. #1
    AllDayRay is offline Cadillac Owners Member
    Automobile(s): 2004 CTS v
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    Clunk

    Could somebody point me to the thread where I could read about the clunk in the
    rear end or tell me what I need to be looking into doing to get rid of it. It Happens when I push clutch in sometimes at cruise or when I first give it a little right foot
    thanks for the help ahead of time. Sorry it's a 04 had it for about a month with
    about 28000 miles on it and I'm in love with it

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  3. #2
    253ctsv is offline Cadillac Owners Fanatic
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    You need new bushings. Probably motor mounts and trany too. Not a bad idea to spend the 7-$800 and get all the revshift stuff IMO. You can search that to get more info if nothing else.

  4. #3
    AllDayRay is offline Cadillac Owners Member
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    Re: Clunk

    So is it 7-$800 just for the parts ?

  5. #4
    darkman's Avatar
    darkman is offline Cadillac Owners Master
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    Re: Clunk

    The clunk in the drivetrain comes from multiple sources. The largest part of the clunk comes from the limited slip clutch setup in the differential and is inherent in the design. This can be seen by turning the drive shaft by hand with the wheels in the air. The driveshaft can be rotated a quarter turn before the wheels begin to turn. Because of this, totaling eliminating the clunk is only possible by replacing the differential with a different design.

    When new, this clunk is masked by other components in the drivetrain. The motor mounts are liquid-filled to soften (delay) the rotational torque to the spring-loaded dual mass flywheel. Both the transmission mount and driveshaft also serve to absorb (delay) some of the rotational torque. The differential is mounted with rubber to further mask the clunk.

    So, if the clunk has reached annoying levels, the common fix is restore the various clunk cloaking devices (differential bushing, motor mounts, transmission mount, etc.) to "new" condition. The permanent fix is to install one of the aftermarket differential setups.

  6. #5
    AllDayRay is offline Cadillac Owners Member
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    Re: Clunk

    So DarkMan with that being said is doing the bushings only a bandaid ?If or I should say when I do the bushing I would be doing the red rev shift ones also would that tighten up handling too ? I want to do things to the V slow over time just want to do the right things first as I want it to last don't want to add any power or anything like that till the weak parts are stronger

  7. #6
    darkman's Avatar
    darkman is offline Cadillac Owners Master
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    Re: Clunk

    Quote Originally Posted by AllDayRay View Post
    So DarkMan with that being said is doing the bushings only a bandaid ?If or I should say when I do the bushing I would be doing the red rev shift ones also would that tighten up handling too ? I want to do things to the V slow over time just want to do the right things first as I want it to last don't want to add any power or anything like that till the weak parts are stronger
    If I understand you question correctly, I would replace whatever is broken first. Typically, the clunk-related component that fails first is the differential bushing, followed by the motor mounts, and then the transmission mount. It should be noted that failed motor or transmission mounts can cause other problems in addition to an increase in the "clunk," such as gear shifting problems.

    When to install other upgraded bushings to improve handling would seem to be an independent decision other than the overlap in the process. For example, if you drop the cradle to upgrade cradle and/or control/trailing arm bushings, it would be a good idea to install a new differential bushing at the same time. But, you may not want to tolerate a bad differential bushing and the increased clunk it brings if the other upgrades are several month away.

  8. #7
    philistine's Avatar
    philistine is online now Cadillac Owners Enthusiast
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    Re: Clunk

    Just a FYI...I've replaced the MMs and trans mount with Revshift and have Delrin bushings for the cradle - I still have clunk and it is annoying. I have not replaced the differential bushing - mainly bc I might replace it altogether for a permanent fix but is costly, even for DIY.

  9. #8
    QwkRhino's Avatar
    QwkRhino is offline Cadillac Owners Member
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    Your have a 2004. It has a very weak differential housing witch has probably been stressed to increase the lash between the ring and the pinion causing the clunk. Replace the differential with a new
    3rd Gen ----- 15793756 or
    4th Gen----- 25873498
    Diff along with the other mods the guys recommend. The clunk should be a lot less noticeable.

    ----------

    Quick tip the SRX diff also works in our cars and seem to be a lot cheaper and stronger the then 1st & 2nd gen diffs. If you get this part # 19178781 GT4 G80 3.73 option and limited slip. You would just have to cut off about a inch off the pinion shaft and swap out the pinion input coupler with your old diff.

  10. #9
    darkman's Avatar
    darkman is offline Cadillac Owners Master
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    Re: Clunk

    Quote Originally Posted by QwkRhino View Post
    Your have a 2004. It has a very weak differential housing witch has probably been stressed to increase the lash between the ring and the pinion causing the clunk. Replace the differential with a new
    3rd Gen ----- 15793756 or
    4th Gen----- 25873498
    Diff along with the other mods the guys recommend. The clunk be a lot less noticeable.

    ----------

    Quick tip the SRX diff also works in our cars and seem to be a lot cheaper and stronger the then 1st & 2nd gen diffs. If you get this part # 19178781 with 3.73 option and limited slip. You would just have to cut off about a inch off the pinion shaft and swap out the pinion input coupler with your old diff.
    The lash between the ring and pinion gear, measured with a dial indicator in terms of rotation at the pinion is only a few thousandths of an inch. To the extent this lash expands over time it still be only a few thousandths of an inch, and therefore does not contribute to the "clunk." The rotational lag in the limited slip setup contributes on the order of a quarter of a turn at the pinion is the real source of the clunk and should not change over time. Confusion on this comes largely from the fact many refer to the rotational lag as "lash" which is actually the correct term only for the ring and pinion relationship, which is tiny.

  11. #10
    AllDayRay is offline Cadillac Owners Member
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    Re: Clunk

    Sorry haven't been on for a little works been crazy thanks for all the info but some of this is like another
    language and I want so much to be working on all this on my own
    Now if you guys where to do this would you put the oem back in it after you did all the bushing or would
    you upgrade the diff and if you would what would you upgrade too
    So you know not trying to build the fast V very just want it to work the most I'm going to do then is a
    Exhaust and hot rod around town some

  12. #11
    darkman's Avatar
    darkman is offline Cadillac Owners Master
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    Re: Clunk

    It is a matter of personal choice, but I would stick with the OEM differential unless and until I wanted to throw on some sticky tires (e.g. drag radials) and go drag racing. You can get by with OEM on the street by launching a little slower and not power shifting.

    (I only have 407 rwhp and I don't have enough traction on asphalt streets for go full bore in 1st and 2nd gear anyway.)

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