Hi guys, I've been driving my 97 LeSabre since it had 23,000 miles on it. It has 70,700 as of today. The car has always had what feels like wheel imbalance above 60 mph, that gets progressively worse as speed increases. I have been through 2 sets of expensive tires since then, and 2 sets of wheels, and that has not made any difference, so obviously I don't have a bad tire, bent wheel, or wheel imbalance issue. I just installed KYB GR-2 struts, which are very firm -- they take the float and roll completely out of the H body ride. The vibration is much more pronounced with these firm struts. I just had the car aligned, and I got a printout of the alignment, w/ specs for everything -- caster, camber, toe, steer ahead, cross camber and caster, thrust angle -- everything is dead in the center of factory spec ranges. I align the car twice a year usually, I'm very finicky about cars being aligned well. Since stiff struts make the vibration more pronounced, it seems to me that the problem is "sprung" -- it must be hanging on the strut/spring assembly, it'* not above it. What else could be causing this? CV axle?? I had the CV'* off the car to do the transmission last week, and the joints felt fine. The drivers side outer joint seemed slightly stiffer than the rest, but by no means was it sloppy or sticking. I have no noise to indicate bad CV axle or bad wheel bearings (could a wheel bearing be causing a high speed vibration but no other problems?) Anything else I missed? The rack is new, so the tie rod ends are new with it. The transmission is also recent, so the problem is not internal to the trans or torque converter. This is driving me nuts now, the vibration is bad enough that the dash shakes above 80. I have my Intense PCM in the mail, which will remove my speed limiter, so I need to get this resolved.

I am thinking either lower ball joints or upper strut mounts. Just guessing based on my expierences.

most places check that before they align it if they are bad the wont align it untill the faulty parts are replaced

bad hub assembly

does the nosie go away when you verve left or right at those speeds?

The strut mounts are new. There is no "noise" associated with the vibration -- it is just a front end vibration/shudder that gets progressively worse above 60mph. The car has done this since it had 20,xxx miles on it, and I'm afraid I'm never going to find the source of the problem.

Those front end vibrations seem to be hard to isolate. I have had the same problem. Moved wheels around, had three different shops attempt to balance, alignment and joint checks, etc. To date I have new tires, new rotors and new hub assemblies. The hub assemblies seemed to make the most improvement. I had one bearing that was starting to growl a little around corners but nothing ever appeared to be loose. My next step will be new tie rods and ball joints followed by struts. At 135k, its not unusual for these components to be worn a bit but I, too am frustrated that no shop can identify the problem.
Good luck and let us know if you have any discoveries.

Thanks Steve. I'm especially frustrated since this car has had the vibration since just about new, and it only has 70,000 miles on it now. The firm struts make the car handle as well as my 77 Camaro, which has all poly bushings. The KYB'* provide an unbelievably firm, controlled ride that I thought was not obtainable with an H body. Unfortunately, the firm struts really let me feel whatever front end vibration it is I'm having.

Unless they haven't been greased regularly,at 70,000 miles it seems too early for ball joints.After reading what you've done and been thru already, it sure sounds like a rotating imbalance, so I'd be suspecting cv axle(*), unbalanced brake rotor.How are the sway bar bushings?

Sway bar bushings are new, since I installed the 32mm solid front bar a couple weeks ago. This is 100% definitely a rotating imabalance, you can feel each revolution in your seat and in the steering. Can CV axles really cause a rotating imbalance, but not make any noise turning? I do drive hard, so I can see a CV axle wearing out prematurely. Brake rotors are new ish, I only get 10k miles to a set of rotors. THe drivers side rotor starts developing grooves on the outside surface after only about 1000 miles, it looks like that caliper may drag -- I had to replace the pass. front caliper because it was dragging probably 20 k miles ago. I will definitely do the caliper in a couple days - I'll be so mad if its dragging on a slightly warped rotor and that is causing my vibration. If this is not the case though, I'm still open for explanations of how CV axles or hubs can cause a rotating imbalance even at low mileage.

Thanks

Front suspension bushings?

What "front suspension bushings" would these be? The car has 70k on it, new struts, new strut bearings, new sway bar, new sway bar end links, sway bar bushings. The lower control arm bushings are as tight as new at 70 k miles. The steering rack is new as of 250 miles ago, and the tie rods are new with it.