driveline thump deceleration
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Cadillac ATS Technical Discussion Forum Discussion, driveline thump deceleration in Cadillac ATS Discussion Forums; Hello. Tried searching but for some reason nothing is coming up. Anyway, I have started to feel a very strong ...
  1. #1
    tahawk69 is offline Cadillac Owners Fanatic
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    driveline thump deceleration

    Hello.
    Tried searching but for some reason nothing is coming up. Anyway, I have started to feel a very strong driveline thump when decelerating under 30mph. When it happens passengers have thought we got bumped or rearended. This is with the auto trans and in factory tour mode and under normal driving conditions. Almost feels like torque converter lock up issues. Any ideas? Thanks

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    Ragtop 99's Avatar
    Ragtop 99 is offline Cadillac Owners Connoisseur
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    Re: driveline thump deceleration

    Is the thump when the car is downshifting?

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    tahawk69 is offline Cadillac Owners Fanatic
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    Re: driveline thump deceleration

    I originally thought the auto trans was trying to hold the gear longer and the thump was a result, but I noticed it happens when coasting to a stop as well right before applying the brakes. So not sure 100% that it's not during a downshift, I will have to watch rpms and pay closer attention.

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    rsingl is online now Cadillac Owners Fanatic
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    Re: driveline thump deceleration

    I don't know how the driveshaft in the AWD ATS is configured but thumps/clunks like this are often due to a dry slip joint if there is one in the drive line. This was an issue with many of the configurations of GMC/Chevrolet pickups for many years and owners that experienced the problem often described it as feeling like they were hit from behind. The simple cure was properly lubricating this joint. Again I have no idea if your configuration has one and crawling under my ATS wouldn't help since I have a 3.6 RWD.

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    Hoosier Daddy's Avatar
    Hoosier Daddy is online now Moderator
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    Re: driveline thump deceleration

    Quote Originally Posted by rsingl View Post
    I don't know how the driveshaft in the AWD ATS is configured but thumps/clunks like this are often due to a dry slip joint if there is one in the drive line. This was an issue with many of the configurations of GMC/Chevrolet pickups for many years and owners that experienced the problem often described it as feeling like they were hit from behind. The simple cure was properly lubricating this joint. Again I have no idea if your configuration has one and crawling under my ATS wouldn't help since I have a 3.6 RWD.
    I never paid attention when changing oil but since these have independent rear suspension I'm pretty sure the diff would be in a fixed location and no need for a slip joint.

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    tahawk69 is offline Cadillac Owners Fanatic
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    Re: driveline thump deceleration

    When it happens It sure does feel like the car gets hit or bumped from behind. Surprised no one else has experienced or noticed this.

  8. #7
    nissanite is offline Cadillac Owners Member
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    Re: driveline thump deceleration

    Just noticed you have all wheel drive. This may be the center differential. Your tires need to be the same size and tread depth. The difference in rolling diameter puts major stress in this part. Had this happen in a shop I worked at. Had worn S rated no name tires in front and new H rated on the rear.
    Make the tire match and this should cease.

  9. #8
    btmasta is offline Cadillac Owners Member
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    Re: driveline thump deceleration

    Maybe the front CV joints going bad.

    Hope my company doesn't make them :/

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