1973 RS LT Z28- chasing a vibration above 40 MPH

Discussion in 'Troubleshooting & Diagnosis' started by Lou6t4gto, Dec 2, 2017.

  1. Lou6t4gto

    Lou6t4gto Veteran Member

    Aug 18, 2010
    Ocala, Fla
    someone asked about the rear brakes, already changed to Rear discs w/ emergency brake. Made no difference. Right now the th350 is out, and a new 700r is bolted in place. new drive shaft made, then came the COLD !
    Brrr, cold, sleet, hell this is Florida !
    So now I guess it will be about a week till the weather gets back to "normal" and I can continue.
  2. Ricks72Z28

    Ricks72Z28 Veteran Member Lifetime Gold Member

    Jan 1, 2005
    I would check your front bearings in the rotor for too much free play.
  3. mce

    mce New Member

    Dec 11, 2013
    Austin, Tx
    If you still have vibrations in your car, check the driveshaft angle. Vibrations can be caused by this being to great of an angle or none at all. Seems,,,, if my memory serves me correctly, you'll need around 1.5 to 3 degrees max. to put the correct amount of preload on the u-joint. Purchase a Bevel Protractor at SEARS, not expensive at all, and do some research on how to set up the angle with shims at Tranny mount or Pinion angle at rear, which will need shims to do that if required. Most likely the rearend should not be a problem, unless the car has been modified in stance. Good Luck and hope you have already fixed the issue! Z/28 Kid!
  4. cnlmustard

    cnlmustard New Member

    Nov 2, 2000
    New Orleans, LA, USA
    I agree you might be ok. I have runout on my stock driveshaft about double allowed. I still need to replace it with a heavy duty type, but it measured straight for years. I took the stock weight off about ten years ago which fixed it, then the problem started coming back again a couple years ago and it's difinitely bent, I don't even need a gage to see it! The cause is likely my extra horsepower twerks it enough to do that. I have a manual tranny too, so it can get torqued pretty hard!

    I hope to see if you get it done!
  5. db468

    db468 New Member

    Jun 23, 2014
    Had/still have vibration in mine found its the rear pinion angle ive shimmed it already but need to go more if youve ruled out tires, brakes, and driveshaft runout/u joints i would look there next
  6. '71StreetZ

    '71StreetZ Member

    Aug 18, 2017
    I've experienced the shakes in my car at both low and high speed the high speeds always seemed to be the drums hanging up and getting super hot since they have been replaced it was fixed but the low speed was actually side to side play in the rear u-joint because the retaining plate had been warped
  7. Chevynut252

    Chevynut252 New Member

    Apr 4, 2016
    Woonsocket, RI
    I have seen this on several G1 Camaro's and everyone has mentioned what I went through looking for vibrations. On a '69 Z with 3:73 gears I swapped tires and then the drive shaft with my other Z that did not vibrate and nothing worked. The differential needed full rebuilding using the same gears but changing shims/bushings and proper set up. That fixed it. My non-vibrating Z did eventually end up with a vibration and that turned out to be broken belts in the tires. Sure, the threads looked new and sidewalls were fine but each time the tires were balanced it lasted less than 50 miles and tires were out of balance again! A new set of tires fixed that one.
  8. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

    Jun 22, 2003
    Endicott, NY
    Honestly, about the only way you're going to find the problem is to put it up on a lift and run it. Obviously, you won't see a vibration if it's in the front end but at least you'll cut the problem in half.
  9. Lou6t4gto

    Lou6t4gto Veteran Member

    Aug 18, 2010
    Ocala, Fla
    well, I've changed from th350 to 700r, and from 2.73 to 3.42. so it still has the "same shake" at the "same speed" but "different rpm's". doesn't that pretty much rule out the drivetrain ? the Only thing that I have NEVER CHANGED in the 43 Years that I've had the car, is the Stock Z28 15x7 steel WHEELS ! they spin true, not bent and don't hop. But is it possible that there is just something about the original wheels that could be doing this ?
    FlaJunkie likes this.

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