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I have a 1999 Olds Aurora with 90K miles that has a long-standing, irregular, vibration problem. I am the second purchaser of the vehicle, having bought it in 2001 when it only had 21K miles.
The vehicle experiences a varying amount of vibration (apparently) from the front wheels at between 73-77 MPH. (No problem is experienced at lower or higher speeds.) The amount of vibration is at its lowest when coasting (neither accelerating nor decelerating) but varies significantly from being hardly noticeable to being consistent to the amount of shake experienced when braking with moderately warped brake rotors.
I have had this vibration problem with three different sets of tires: 1) the OEM Michelins, 2) a replacement set of Dunlops, and 3) the current Goodyears (which were provided via a factory “adjustment”.) The problem is better (but still persists) after a “standard” computer tire balancing but will completely disappear (for a few thousand miles) if I have the tires “road force balanced” by my local Cadillac (formerly Olds) dealer. However, this balancing costs $20 @ tire and is hard to justify on an ongoing basis.
The Cadillac/Olds dealer simply indicates that Olds Auroras (and similar GM vehicles built on this platform) tended to be more sensitive to tire balance than most vehicles and I simply need to invest in the road force tire balances. Is it possible that a broken motor mount and out-of-balance axle shaft could be causing this problem? Is a small amount of side-to-side rim variance (described below) enough to cause this problem?
Additional factors of note include the following:
1) When I originally purchased the vehicle and checked with Olds to see what (if any) warranty work had been performed on the vehicles, I discovered that 3 or the 4 original Michelin tires had been replaced to address a vibration problem;

2) The vehicle has the OEM optional factory alloy (chrome) wheels. When the local Goodyear dealer installed the current set of tires, they indicated that two of the rims had a small amount of side-to-side run-out, with the worst varying by amount 1/16<SUP>th</SUP> on inch;

3) I have replaced the front rotors once and resurfaced the rotors a second time without any impact on the vibration problem.

Any suggestions would be appreciated.
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A broken motor mount would cause much worse vibration, and would be present over a much wider speed range.


Does the vibration occur on any road, or only at a certain section of road?


Find out which 2 rims had runout, and put them on the back. See if that changes your vibration. Then put them both on one side and see what happens.


Brake rotors warping is a common GM problem, but in your case is not causing your vibration. Rotor warping vibration is only present when braking, and occurs at any speed.


I would look at suspension parts next. Maybe there is some wear or looseness. I am not a suspension expert, so get someone who works with it a lot to check for you.


By the way, excellent description of your problem-you included all the necessary details, in a clear and concise writeup.

 

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Thanks again for the additional suggestions.


Henry
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One thing im sure it could be is the wheel barings or they lugs may not me tight enought or tire was not set right.
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Try this although it is a little labour intensive.


Mount your silly spare at each wheel position to see if there is any improvement. You may be able to isolate the one wheel/tire assemblythat is causing the problem.


Your silly spare should have 65 pounds of air pressure.
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