First post -but the forum has been very helpful with stuff I researched here in the past.

Problem is in my '84 coupe. The car was in storage for about nine years, and when I took it out and drove it from Vegas to FL it had developed a vibration at speeds over 65mph. It gets worse, and WORSE, as speed increases - and I haven't tried it over 85 (it's way too spooky by then). I have tried multiple tire balancings - and two complete tire changes. No help. Car has only 53000 miles and is excellent otherwise. Front bearings tight, rear wheels have noticeable play (both about the same), but not really excessive I think. All parts are originals. No noticeable play in drive or half shaft universals.
I'm thinking some part has become warped from the sitting (in storage in Vegas - very hot) and causes the increasing vibe as speed increases. I'm looking for the most likely causes to start checking. Suggestions?

 

Where do you feel the vibration ? Maybe a bad motor mount?

 

Thanks for the reply. Vibration is most apparent in the steering wheel but is visible at hood too. Motor mount is interesting thought as sitting in storage could seemingly affect it. Will check it. Bruce

 

do you get any surging when lightly applying the brakes? you can get vibration from any of all 4 wheels if rotors are warped.

 

My bet, after changing tires, even though it has low miles you have shot halfshaft u-joints. Get it up on a rack and look really close at the crosses of the u-joints and look for any sign of red. If you see any it a sure bet the rollers are dust. Took me a while to figure it out the first time...
Do all 4. A search will show you the ends and outs. Doable in a Saturday without much trouble. Don't get greasable u-joints.
I've done mine twice is 20yrs on my 87.

JS

 

OK, more stuff to check. May take a few days, but I'll post back what I find. Thanks, Bruce

 

Well, it's not the motor mounts or the rotors. New medical issue prevents me from further checking the halfshaft ujoints for awhile. Until then it is a 65mph vette....thanks again for the suggestions. Bruce

 

I'd bet flatspotted tires. When you said that you changed tires, did you install new tires?

 

Also check the shocks. No matter how tight and round everything is, the suspension will bounce like a basketball without proper dampening.

 

If it's indeed from the fronts,
1. grease the tie rod ends. If the grease makes a difference, the last owner may have driven the car a lot with the tires needing air, causing undue wear on the tie rod ends.
2. pull the wheels off, and check the back of the turbine blades on the wheels for cracks. Some of the early wheels cracked on the little "spokes".
3. add 5 PSI to the tires. if it goes away, then the tires need more air due to the higher tech compounds in the tires.
4. take off the shocks, and check out the upper shock bushings. They are a complex affair, and may be worn.
5. How far are you driving this thing? you may have "morning sickness in the steering rack. Morning sickness refers to a rack that has an internal sealing problem that goes away when the fluid gets hot.
6. You might try "road force balancing". It costs a little extra, but you will know that it's not the tires when you are done.
7. Check the wheels by jacking up the car and setting up a dial indicator.
Have the dial indicator on the flat bead area, and slowly rotate the wheels, and watch the dial. If you have more than .005, yoiu will feel it. check all 4 wheels.
8. Check the bushings that mount the front rack. One bolt is the mount, and the other side is a clamp. make sure both are tight.
9. have someone drive alongside of you on the highway, get in the middle lane, talk to them on the cel phone, and have them tell you what's happening at different speeds. First on the left, then on the right.

FOR THE REAR:
1. check the runout on the wheels.
2. check the u joints.
3. check the rear wheel bearings
4. check the rear shocks
5. check that the half shafts do not have any dents, dings, etc.
6. put the front tires on the rear and see if different parts of the car vibrate.
7. check the tires for age. old tires will take a set and vibrate.
8. Check the rubber on all bushings, especially the dog bones.
9. make sure the bolts on the C beam are tight.
10. Check the bolts that attach the half shafts to each end.

There, that will keep ya busy.