Vibrations at speed and other issues

1998 Trans Am, A4, completely stock, 75000 miles
I have what might a few seperate problems, or maybe all related.
1. At between 60-75 mph, I get a pulsing vibration through the
steering wheel. If I hold it tight I can barely feel it, but when holding it lightly there is a fairly significant wobble. Doesn't do this all the time (and some days are worse than others). I thought this was wheel balance, and so had them re-balanced a couple of times, including once after replacing the rims with another (standard 16x8) set. Tires are BFG KDWS 245/50 and these were also replaced to no effect. When this happens the interior visors can sometimes be seen wobbling. This was worse to the point that I could feel it through the seat before I replaced the rims.
2. At above 40 mph there is a quiet grinding sound from what sounds like the wheels. This happens whether the car is under load or in neutral. Seems to get louder with more speed.
3. The steering sometimes feels light.
4. If I look at the car on a level surface from the front, it does not appear to sit straight. The passenger side appears a little lower than the driver side.
The first problem has been present since I bought the car a year ago. None of these are big problems right now but I'm concerned that a problem may be starting to appear and if it's suspension related I'd rather catch it now before a catastrophic failure!
Would appreciate any clues as to what might be the problem or problems here.
Thanks. Keith
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Sounds kind of like it might have been wrecked and they didn't do a good job on the frame. Jack the front wheels up and make sure everything is tight, ball joints, wheel bearings, linkage, etc. Check the brakes for wear or looseness. Finally, have someone follow you and see if the car is tracking straight and doesn't have a sprung frame, which will make it drive slightly crooked down the road..

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Check brakes & calipers arn't seized/stuck/worn especially the handbrake cable or that the rotors are OK and not warped.

I have read that they sit that way so they appear level with a driver in the car. Can't say I've noticed it on my Z28 though., so can't say how accurate that may be.
Also check the rear trans mount isn't split.
HTH
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Mitch - 1995 Z28 LT1 M6 terminal snipped-for-privacy@sand-hill.freeserve.co.uk
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