Rear Diff Solution - Is there one? HELP Please.
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2004-2007 Cadillac CTS-V Performance Mods Discussion, Rear Diff Solution - Is there one? HELP Please. in Cadillac CTS-V Series Forum - 2004 - 2007; I am starting to drive my 04 V more often. The car is low mileage and perfect except for driveline ...
  1. #1
    pjcnlv is offline Cadillac Owners Member
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    Rear Diff Solution - Is there one? HELP Please.

    I am starting to drive my 04 V more often. The car is low mileage and perfect except for driveline vibration and noises.

    I NEED SOME HELP HERE...

    The car is stock except for the dealer provided, Borla catback exhaust and upgraded brake rotors.

    The rear diff and trans to dif, driveline have been replaced under warranty.


    Here are the symptoms:

    * Oscillating groan from rear end when backing around turns and often when going forward in tight turns. It seems to be less once the car warms up. I suspect that this is from the differential clutch pack and perhaps the wrong oil in the diff.

    * Nasty harmonic vibration under light to feather throttle load in 6th gear at 65MPH to @75-80 MPH. There is zero feedback of this vibration in the shift lever. The vibration is enough to blur the rear view mirror vision and it is very audible in the rear seat. The vibration is much less intense in 5th gear at the same speeds.

    I'd really like to learn of a solid, aftermarket upgrade to this common problem on this car.

    Any and all help is appreciated.

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  3. #2
    Twitch's Avatar
    Twitch is offline Cadillac Owners Connoisseur
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    Re: Rear Diff Solution - Is there one? HELP Please.

    First thing I would do is change the fluid in the diff to a heavier weight.
    Vibration could possibly be that the drive shaft was not re-installed properly. Are you sure it's not from the exhaust?
    Well, that's my .02 anyways.

  4. #3
    odla's Avatar
    odla is offline Cadillac Owners Connoisseur
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    Re: Rear Diff Solution - Is there one? HELP Please.

    I had what you describe at 70k miles. i changed the read diff fluid. took care of it.

  5. #4
    rand49er's Avatar
    rand49er is offline Cadillac Owners 10000+ Posts
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    Re: Rear Diff Solution - Is there one? HELP Please.

    I might be wrong, but before you change to a different weight lube, I can tell you that five years ago guys here were reporting that inexperienced dealers were neglecting to put the anti-slip additive in the diff when they changed the fluid. The symptoms you report were similar to theirs.

    Get hold of C66 Racing and get some his Amsoil Severe Gear 75W-90 in your diff. I also put a bottle of the Slip Lock additive in, but I think it already includes it. MUCH cheaper swapping out the fluid than slinging a wrench and tearing into the diff needlessly. Just my $0.02.
    '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
    pjcnlv is offline Cadillac Owners Member
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    Re: Rear Diff Solution - Is there one? HELP Please.

    Quote Originally Posted by odla View Post
    I had what you describe at 70k miles. i changed the read diff fluid. took care of it.
    Thanks..
    Did the fluid change help the groaning noise or the vibration or both?

  7. #6
    Twitch's Avatar
    Twitch is offline Cadillac Owners Connoisseur
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    Re: Rear Diff Solution - Is there one? HELP Please.

    Quote Originally Posted by rand49er View Post
    I might be wrong, but before you change to a different weight lube, I can tell you that five years ago guys here were reporting that inexperienced dealers were neglecting to put the anti-slip additive in the diff when they changed the fluid. The symptoms you report were similar to theirs.

    Get hold of C66 Racing and get some his Amsoil Severe Gear 75W-90 in your diff. I also put a bottle of the Slip Lock additive in, but I think it already includes it. MUCH cheaper swapping out the fluid than slinging a wrench and tearing into the diff needlessly. Just my $0.02.
    I've got 15k miles on my Amsoil diff fluid. No additive, and no problems either
    As soon as I can figure out which diff bushing to go with, I'll try the higher weight stuff.

  8. #7
    CadiBlk's Avatar
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    Re: Rear Diff Solution - Is there one? HELP Please.

    Isn't there a tsb or something for that 6th gear vibe?

  9. #8
    pjcnlv is offline Cadillac Owners Member
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    Re: Rear Diff Solution - Is there one? HELP Please.

    Thanks again but can you be clear on the fix:

    Did the diff fluid change solve the groaning, the vibration or both?

  10. #9
    CancerJCC is offline Cadillac Owners Connoisseur
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    Re: Rear Diff Solution - Is there one? HELP Please.

    Quote Originally Posted by pjcnlv View Post
    Thanks again but can you be clear on the fix:

    Did the diff fluid change solve the groaning, the vibration or both?
    It is to difficult to tell you yes or no for your specific application. Your "groan" may be my "squeak" while Tony's "rattle" might be your "vibration". Get my point? Just upgrade your diff fluid with Amsoil (PM C66 Racing for dealer cost) and then go from there. Fluid is cheap and easy and where you should start.

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