Vibration at 75MPH crusing, Not in steering wheel, not due to wheels or tires

Just bought a 2002 Buick Lesaber 30K miles. Had rear tires replaced due to cupping. Have replaced tires and wheels from car that did not vibrate. Vibration at 75mph is still there. Machanic tells me he
doesn't know what he can due to solve the problem. Since the steering wheel does not vibrate does that mean the problem is in the rear of the car? Could it be an alignment problem? Give me some suggestions that I can propose to my machanic to check. Would wheel bearings cause this problem? thanks tom
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snipped-for-privacy@dva.state.wi.us wrote:

Wheel bearings is possible. See if you can find someone with the abitly to high speed spin balance the wheel/tire assembly on the car to see if you can reproduce the vibration and track its source.
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There is a GM tsb that might pertain to this problem, 00-03-10-007 feb 04. Check with a Buick dealer to get the full info.

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How can I get a summary of what this tsb is about all I know is it is suspension related. It has a NHTSA# 10011691 and service bulletin# 3249
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Actually your dealer must make this available by law to the general public if you have a vehicle that may be affected, he can charge you a small copying fee. Alldata provides a complete online manual with all the tsb data, 24.95 per vehicle.

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On 22 Sep 2005 11:36:38 -0700, snipped-for-privacy@dva.state.wi.us wrote:

Cupping sounds like bad (like completely gone) shocks to me. Bad shocks certainly can cause a vibration at certain speeds.

I would agree with other post about finding someone with a balancing machine that can do them ON the car. Either this or a shop with a dyno. This effectively mimics being on the road and they might be able to see something then.
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