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Classic/Antique Car Repair/72 chevy truck vibration

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Expert: - 11/10/2009


Question
Hi Vern, I have a 72 chevy cheyenne, 350 4bl carb   I noticed a harmonic vibration in the cab as I'm driving on at highway speeds=especially at 59mph. I've had the tires balanced, the drive shaft balanced, motot mounts and transm. mounts all checked ok, and also had it tested on a dyno,  No one can find the source of the vibration. I did notice the problem after I had new poly body bushings  installed, replacing the original rubber ones. The mechanic said that it is not the problem.I'm thinking that poly is too stiff, and the rubber ones would have absorbed more vibrations. Am I overlooking any other vibration source? should I replace the poly mounts?  Thanks, Bob

Answer
Hi Robert:
You have identified almost all the sources of possible vibrations, so I tend
to agree with you. Polymer bushings are stiffer than rubber. However, Have you
had the ball joints checked? Any play in the ball joints would exhibit the
same vibration as a miss-aligned wheel at high speed.

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Vern Bullock

Expertise

Visit my website at: http://www.classytransportation.com/ I can answer most questions about autos built in the 60's 70's and 80's. Specifically, Lincolns, Rolls Royces and the Excaliburs. Mechanical issues and technical questions are my expertise. I also have a general knowledge of most older automobiles. Keep in mind, I can only provide answers if the questions are very specific and complete. Without details, I can only speculate and that's not good for solving your problem.

Experience

I have owned and maintained Silver Shadows for over 10 years now. I find most mechanics and even Rolls Royce mechanics have very little knowledge about these automobiles. I have researched these cars in quite a bit of detail and can pretty much tell you what is wrong, if you can describe the behavior in detail. I have saved quite a few RR owners a lot of money and aggravation due to improper diagnosis. I am the owner of Classy Transportation, LLC a luxury limousine service specializing in antique cars, classic cars, vintage cars and exotic cars.

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Classy Transportation, LLC Limousine Service.

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All around the Internet

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I hold a BS degree in computer science and a MS degree in mechanical engineering.

Awards and Honors
I regularly compete at car shows and average around a dozen awards annually.

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See Web site at: http://www.classytransportation.com/

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