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94 convertible vibration

Discussion in '1994-2004 V6 Mustang Tech' started by hemiguy, Nov 3, 2016.

  1. hemiguy

    hemiguy Member

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    Hi Everyone.
    I'm the second owner of a V6 convertible 5 speed that has never been hit or modified.
    It has the vibration that is described in TSB 615327. It starts at 62 mph and is awful at 65, it smooths out a bit after 75, but you can't really drive at 75 all the time!
    The vibration has been there as long as I have owned it (eight years). I know its not the wheels or tires, I have two sets of wheels and tried three sets of tires, all balanced of course.
    Luckily my commute is 5 miles, so I don't experience the vibration that much. But last weekend I drove 100 miles or so at highway speeds and it was very annoying to say the least.

    My question is, since Ford put out a TSB, did they ever have a definitive solution for it? I have searched everywhere but cannot find one. If anyone knows I would appreciate the information.
    I am planning on doing a major overhaul of the car since its 22 years old and I want to fix the vibration if I can. If I can't then I may just unload it.

    Thanks!


    This is the TSB:
    • Date Reported DECEMBER 01, 1998
    • NHTSA Reference #615327
    • TSB Reference #5132
    description: SOME GT CONVERTIBLES MAY EXPERIENCES VIBRATION / SHAKE WHEN DRIVEN ON SMOOTH ROADS AT CONSTANT SPEEDS AROUND 62 MPH / 100 KPH. THE CONDITION MAY BE DUE TO HARMONIC RESONANCE BETWEEN THE ENGINE, BODY AND SUSPENSION.
     
  2. Phil II

    Phil II Cone Destroyer Staff Member

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    Check out the engine mounts, transmission mount, control arm bushings, and the driveshaft u- joints.
     
  3. 6 Shooter

    6 Shooter Well-Known Member

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    My vote is for the U-joints as they dry up over time and begin to bind. Based on the age of your car, all original rubber bushings are probably dry rotted, hard, and have lost their elasticity. They are at a bunch of locations, engine mounts, rear transmission mount, top and bottom control arm bushings, tops and bottoms of front and rear shocks, exhaust hangers, etc. Would start with new U-joints which can be done in the driveway and jacking up the car. Then, test drive the car to see if issue is resolved. While under the car, you can inspect the exhaust hangers. The control arm bushings are mainly for rear end alignment from side to side and front-to-rear twisting, not necessarily related to vibration. Have you checked the true alignment of the front and rear wheels to make sure they are not bent from a street bump or curb hit?
     
  4. John D. Carter

    John D. Carter Member

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    The motor mounts should not be that hard to replace. If you can do it yourself it would not be that expensive either. I think I would give that a shot. Certainly could not hurt.
     
  5. Flex

    Flex Kicker of Arrogant Asses

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    Most likely the drive shaft. Generally when the vibration is at a specific speed and that throughout the range, it will be the drive shaft. My sc was showing the same vibration at the same speed. The drive shaft was not balanced properly after it was shortened.
     
  6. hemiguy

    hemiguy Member

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    Hi Folks, thanks for the suggestions.
    I think I will pull it into my garage for the winter and go through it. Its about time for an overhaul anyway.
    I'll report back next spring!
     
  7. Gerry Smolynecky

    Gerry Smolynecky New Member

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    I purchased last spring a 1998 Mustang conv. and have already invested $2000 to find vibration problem without succes.
    I have now purchased 4 new tires to be installed this spring, as the car is now stored until 1st May.
    My vibration also starts at approx 62mph and ends at 70mph.
     
  8. fasterthanyou

    fasterthanyou Active Member

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    Tires/wheels and driveshaft u-joints are about the only things that will cause a vibration at a specific mph range.
     
  9. hemiguy

    hemiguy Member

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    Hi Gerry.
    Finally, someone who is experiencing the same thing. What have you tried so far?
    I'm not sure tires will help, I tried two sets of wheels and three sets of tires with no change.
    The Ford tech bulletin says its a harmonic resonance, but they don't say how to fix it!

    Good luck,
    John
     
  10. Gerry Smolynecky

    Gerry Smolynecky New Member

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    basicaly changed the whole front suspension, 4 Wheel alignment, drive shaft has been checked for balance, wheels checked for possible dents, well balanced , tire rotation and still vibrating. Will change all 4 tires this spring and will also check all rubber componets.
    Did about 7000km this summer, really enjoyed my first convertible. 50% below 60mph and 50% over 70 mph so did not suffer too much of the vibration. They tolerate up to 73mph on highways here, so I have been Lucky.
     
  11. Flex

    Flex Kicker of Arrogant Asses

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    Have you checked for broken motor mounts and transmission mounts?
     
  12. Gerry Smolynecky

    Gerry Smolynecky New Member

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    Not yet, but when changing the tires this spring, it will be done. It's my next step.
     
  13. John D. Carter

    John D. Carter Member

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    My 98 coupe with high mileage is now doing the same thing. It does seem like some type of harmonic resonance. I put lowering springs on and also all new Energy Suspension Bushings on both the front and rear suspensions. Not sure if that is related to the problem or not. I will change the motor mounts and report back.