Thumping noise under car around driver seat. ?

2011 GMC Acadia. 

Makes thumping noise only when starting to accelerate from a stop and letting off the gas going slowly around 10mph. Also it's only when in gear. In park, revving it doesn't make a sound. Also can't seem to hear it at any higher speeds than just taking off. Looked under and didn't see anything out of the ordinary. It's sounding like it's between the driver seat and seat behind it. I feel like I have a bowling ball banging off my seat almost. Any ideas? 

3 Answers

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  • Geo
    Lv 6
    2 months ago
    Favorite Answer

    That sounds like a bad Motor or Transmission mount. Have someone look at the engine and go between Reverse and Drive with the brake on. If the engine moves a lot you have a broken mount, where the rubber is no longer attached to the steel part. The only other thing could be a broken exhaust hanger that is letting a pipe hit underneath.

  • Anonymous
    2 months ago

    Would have the tires checked....as it is a rotational noise.  To be sure, find a road that is light with traffic and take it up to speed then shift into Neutral.  Is the noise still present while you are coasting? Then I am betting tires. Maybe one has a chunk missing or failed in some other way.

    . Slip the shifter into Drive and continue driving.  You can do this and no harm happens to the engine.

    Other than that, see a mechanic who can see your car and advise.

  • donnie
    Lv 7
    2 months ago

    Take it to the repair shop

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