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Weird vibration manual swap

Discussion in '1994-2004 V6 Mustang Tech' started by IRA, Feb 2, 2018.

  1. IRA

    IRA New Member

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    Got a weird issue for you guys. 2002 v6 just completed a manual trans swap. Now I've got a nasty vibration that starts at 65 mph... But only in 5th gear. When I'm in 4th gear the vibration is very minimal. When I shift to 5th and get up to to 75 it makes a loud noise and a nasty vibration. The faster I go the worse the vibration and louder it gets. Noise seems to be coming from the engine almost sounds like a bad misfire but the rpms aren't fluctuating. No check engine light. I can count the rumbles (80 rumbles every 50 seconds or 1 mile traveled @75mph). By the time I get to 80 mph the rumble is constant. I suspect a bad 5th gear or u-joint. (Junkyard t5 and drive shaft). Any thoughts?
     
  2. IRA

    IRA New Member

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    Fyi 2nd hand syped snow tires, junkyard clutch and flywheel. The noise goes away when accelerating, and coasting, noise and vibration are only when cruising at 75mph plus. (Would suspect bad differential except it was fine before manual trans swap).
     
  3. Phil II

    Phil II Cone Destroyer Staff Member

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    You may have altered the angle the u-joints were worn to function at due to the transmission swap. As your problem occurs only above a certain wheel speed it's not likely transmission forward.

    What happens in 5th below say 45 mph?
     
  4. IRA

    IRA New Member

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    Purs like kitten no vibration at all
     
  5. IRA

    IRA New Member

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    U-joints replaced did not make a difference at all, Also I swap the front yoke off the junkyard driveline to my original driveline to eliminate any possible bent driveshaft or imbalance
    Any other Ideas guys?
     
  6. Sam36

    Sam36 Active Member

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    If it only does it in 5th gear I'd say something is wrong with 5th... I've heard some after market transmission mounts or rear end bushings can sometimes cause weird harmonics but can't quite remember the details of it all.