Hey guys,

This is a question for my 89 Vette. Already posted on the corvette forum but I am getting some pretty varied answers.

My girlfriend regularly drives the cars,... I take it out on the weekend. We put alot of miles on all of our cars, I love to drive my toys. Took the car last weekend, and I noticed a heavy vibration that I could feel throughout the car beginning at around 70MPH and going around to 85MPH. As speeds pased 70 it got worse.... I specifically felt it in my seat. I thought she my have hit a pot hole so I went to a friend and had the tires balanced properly, and torked back on the car at 100 Ft/lbs. Same vibration.

I was told on the corvette forum that I have Z rated tires and if the car sits to long flat spots form (that I didn't know?) But this past weekend I put about 500 miles on the car with no improvement.

I am thinking it could be Universal Joints (OUCH THE CAR HAS ALOT OF THEM) or Wheel Bearings. I am not sure which one? Maybe its something else?

What do you guys think??

DG

U-joints will typically vibrate more under load (acceleration) and the vibration will almost go away when coasting.

Whats the best way to test to see if its a wheel bearing? What gets me is normally when a wheel bearing goes you hear a sort of grinding/whistling (a different whistle from a differential) that comes out of the rear. This is JUST a vibration. Its a serious vibration but yet no grinding sound???

Price of wheel bearing is $182 Per Side !!!!!!!!!!!!!!!!!!!!!!!!


DG

Have you got under the car and looked at all the suspension and steering parts to see if anything is bent, loose or missing? When was the last time you had the front end aligned? There are to many things that can cause a vibration to give a direct answer as to what is causing it. As far as Z rated tires forming flat spots, this would be from very long term storage, I have Z rated tires on my chevelle and it is stored for up to 5 months during the winter, and I have never had any flat spot problems on my tires.

i've had vibrations like that, and sometimes they go away if you just grease up the u-joints. of course, i've never had a car with more than 2 of them..
but if the grease gun makes it go away, then you probably have some u joints on their way out.

How old are the tires? Could be a belt that's shearing from a pothole, etc.

Do a quick tire swap to eliminate the possibility and you'll be able to focus on the other stuff.

Possibly could be a driveshaft out of balance. I had a similar issue on my chevelle.

i've had vibrations like that, and sometimes they go away if you just grease up the u-joints. of course, i've never had a car with more than 2 of them..
but if the grease gun makes it go away, then you probably have some u joints on their way out.

You know,... I didn't even think to do that! Thanks, that would be the easy way to check out the U-Joints... I will try that this weekend and let you know.


How old are the tires? Could be a belt that's shearing from a pothole, etc.

Do a quick tire swap to eliminate the possibility and you'll be able to focus on the other stuff.

I thought that might be a problem so I took off all 4 rims and inspected them. Everything looks good, but to be sure I will swap those rims with the one on my Impala and take her out for a spin. It wouldn't surprise me if a belt did go. This would be the THIRD TIME (different cars) that this has happend to me. The reason I didn't swap the tires yet was because, when I visually inspected the last two sets there was a bulge in the middle that look like a mountain had imploded. This is not the case this time, but hey..... its worth a try anyway,....

Thanks for the ideas,... Ill post if I solve the problem this weekend.

Dan

I'll bet you a nickel its just tire balance. All vibrations have very unique and individual characteristics that help with diagnostics. Tire balance issues always start at ~65ish and you can drive through them by 75ish.

Tire belt issues are low speeds and feel like something is loose or "squirm".

Driveline issues are load related regardless of speed.

Wheel bearings won't "vibrate". They are easy to check, just jack up the wheels and place you hands at 12 and 6 o'clock. If can feel any perceptible movement, they are worn.

I can't believe it.... the tires did infact flat spot from sitting out in the cold!!!! Who would have thought...

I swaped a set and the car rode fine... who would have thought???

DG