Hi guys, I thought I had fixed the high speed vibration on my 97 LeSabre, that is, until I had to take it on a 4 hour trip home for spring break. The vibration feels like a rotating imbalance -- it is definitely speed dependent, and the shaking has a frequency proportional to road speed. I can drive 75 mph and have a very strong vibration which shakes the car seats, steering wheel, dash, hood, etc, and at 80 mph it will be smooth. There seem to be harmonics above 50 mph at which the vibration is the worst.

Here'* what I have replaced to try to correct this situation:

Wheels -- I have my 4 original alloy wheels on the car now. I had 4 other wheels, and was afraid they could have been bent, so I put the original wheels back on. I had both sets of wheels rebalanced twice each at different tire shops to make sure some kid wasn't improperly balancing.

Tires -- I have brand new front tires on the car I borrowed from my friend. Although my Toyo'* are high quality, fairly expensive tires with low mileage, I wanted to check anyway to see if a bad tire(*) was the problem. It wasn't.

Struts are new within a few thousand miles, and strut bearings are new.

Steering rack. This isn't related to the vibration, but its new and tight anyway

Tie rod ends (both) and drivers side ball joint (I damaged the boot on the driver'* ball joint and replaced the whole thing for the hell of it)

Alignment -- the car has been aligned 3 times in the past 2 months, at different places. All of the alignments show perfectly in spec for all criteria

End links and sway bar bushings are new

CV axles -- I replaced both CV axles, driver'* side with a Dayco reman axle, pass side with a 20k mile original axle. No change in vibration (I was really banking on this being the problem too)

Rotors -- rotors are brand new made in USA high quality rotors

Calipers are both new remans and are not dragging

Wheel bearing/hub assemblies. Both replaced, brand new.

I am completely out of ideas as to what could be causing such an extreme high speed vibration. The car has 73k miles on it and has had this vibration as long as I can remember (I've had the car since ~22k original miles), but it'* much more pronounced now with the KYB struts transmitting the vibration to the body.

The transmission and torque converter have only 33,500 miles on them (I replaced them). I tried shifting into neutral at speeds when the vibration is really bad, and this did not diminish the vibration, so it doesn't appear to be a torque converter/trans related issue. The vibration usually becomes worse when I let off the gas. Also, ascending long gradual hills at high speeds (over 60 mph) seems to make the front end vibration much worse.

The only thing I can think of is that the position of the engine is shifting under power/decel and this is causing the axles to form weird angles that cause a vibration at high road speeds. It'* not like this car has a ton of miles on it and would have worn out mounts or suspension bushings, so I'm stumped. When I had the trans out, the mounts all looked good, but that doesn't prove anything for sure. Which motor mount should I replace first if I think the motor is torquing over and causing the axles to reach critical angles?

Any other suggestions are appreciated, as I am honestly going to sell this car soon if I can't get rid of the vibration. It feels like you are sitting in a massage chair above 50 mph, which I can't continue to live with. This was my grandfather'* car and I'd much rather keep it than get something else, but at the same time I have spent a small fortune maintaining it (probably exceeding the $8,000 I paid when I bought it from his estate) and it still has the front end vibration.

Geez, what a stumper! You've already replaced and checked out the list of usual suspects. What is left that is affected by rotational forces? Only thing that comes to mind is wheel bearings. Usually the complaint is noise, though, not vibration. I'll think on it some more and see what, if anything, else I can think of.

Oh yes! I forgot. I replaced both wheel hub/bearing assemblies as well! They are brand new parts.

Thinkin some more.

I would still say it has something to do with the tires. With that said.....

There are some specialty shops that cater to hard to solve balancing issues so they balance the tires while the wheel and tires are mounting on the car.

http://www.fostertire.com/tcm_blnc.htm

Ol' Timer, you are correct in that it definitely still seems to be a wheel balance issue. I can drive through the vibration. At over 80 mph, the vibration becomes minimal. Over 100 mph it is nonexistent. This sure sounds like wheel balance to me. What kills me is that I replaced the wheels, and replaced my expensive tires with another brand new set of good quality tires. I've heard of on car dynamic balancing before, but I don't know who does this. I'm in the Philadelphia area. Heck, I'd drive hours each way if that would fix my vibration forever and I could enjoy my damn car instead of dreading driving it.

Could be something as simple as improper torque on the wheel studs....also reman axles are usually just used axles with new boots and grease....the alignment shop that used to be next to my work used dynamic balancing....ie using a drum/motor to spin the wheel/tire assembly up to speed....

I torque the lug nuts with a click type torque wrench. I also took the reman CV axle out after running on it for a short while and noticing that it didn't improve the vibration, so I have the stock 73k mile axle on the drivers side and a 20ish k mile axle on the pass. side. My tires are dynamically balanced (I think all shops do this now) but dynamic on-car balance is a completely different issue, where they balance the wheels on the car, taking into account driveline imbalances.

If you haven't already done so, check the engine mounts under load. Block the wheels, hold the brakes and see how much the engine shifts when power is applied. Forward and reverse. If you have a bad mount you should see it. My two cents, worth price charged.

Hey Ghost, which mount do you think would be tending to wear first, the dog bone underneath? The rear drivers side mount is self limiting and doesn't have much room to move, and the front drivers side mount is just the damper. The upper pass side mount is huge-mongous. How much movement is "normal"? The engine definitely torques over when you rev it, but it'* designed to have some movement since the front damper exists.