350TH High RPM thump coming OFF gas

Discussion in 'Transmission & Driveline Topics' started by wwest, Sep 24, 2015.

  1. wwest

    wwest Veteran Member

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    Just found a thump/bang coming OFF the gas at high rpm that I think is coming from my transmission. I feel it in my feet.

    Absolutely no issues at low RPM. Shifts great. Shifts great at high RPM too....
    Goose the throttle here and there at lower RPMs - nothing.

    Stab the throttle, go through the gears to about 4k and yank your foot off the gas...In drive. Bang. No other issues.
    At 3k its more of a thump.

    Maybe a high pressure disengage problem?
    Maybe not the tranny? Maybe motor mount or suspension.....
    It seems more pronounced on a loooonnng pull through rpm.
     
    Last edited: Sep 24, 2015
  2. Dave Nelson

    Dave Nelson Veteran Member

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    First I would check motor mounts, U joints, trans mount.
     
  3. wwest

    wwest Veteran Member

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    I agree, in talking it to death with everyone this morning that's the consensus.

    Looks like I know what Im doing tonight....lol
     
  4. JONESYFXR

    JONESYFXR Veteran Member

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    I'm onboard with the others...trans or motor mounts. Check the crossmember too.
     
  5. wwest

    wwest Veteran Member

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    Well, jacked up the motor...mounts held solid. Motor and tranny.

    Im going to put a go pro under the hood this weekend and check it that way.


    It really sounds/feels like its the transmission disengaging. Like its banging into a freewheel status.

    But Im not giving up on mounts.

    More this weekend
     
  6. GoldenOne7710

    GoldenOne7710 Equal Opportunity Offender Lifetime Gold Member

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    You may not find a broken mount by just jacking up the enigne. You need to foot brake it while applying moderate throttle and have someone watch the engine/trans movement under a load. Try it in forward and reverse.
     
  7. wwest

    wwest Veteran Member

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    OHHHH I like that idea.

    I am thinking its ripped at the top and it takes time and TQ to squeeze it through. Then off the throttle it drops a half an inch and bang.

    Ill find out soon - and let you know.
     
  8. Marv D

    Marv D Veteran Member Lifetime Gold Member

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    Wade check the U-joints too.

    Your putting some decent torque through that trans,, it wouldn't surprise me if you have torn up some thrust shims and it's wanting to come apart. How long has it been since the trans was freshened?

    Also arent you running solid body mounts? (just another thing to check)
     
  9. 496z28

    496z28 Veteran Member Lifetime Gold Member

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    Loose torque converter bolts?
     
    Last edited: Sep 25, 2015

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