tnsg

I have a 1992 LT1. I have had this problem for several years and have gotten frustrated and not drove it much. The problem first started that the ride would be fine and then suddenly it would ride as if you had a flat tire, stop and no flat tire and then proceed on. This would happen at various times and some times not at all. So I have went through replacing tires, shocks and most recently the rack and pinion. I went for a drive yesterday for several miles it was fine and then suddenly it begins to ride like the tires are not round. It did not ride as if the tire was flat but very rough ride. Next time you take it out, it maybe fine for a while and then start again. I am lost on what to do, my local mechanic does not know what it is. I talked to a corvette dealer and have not been of any help. Could it be as simple as an alignment, but it does not do it every time you take it out? Any suggestions or if anyone has experienced this issue would be greatly appreciated .

81c3

Are the wheels and tires original and in original sizes?

From your description, not an alignment issue.

Check wheel bearings. Check rear 1/2 shaft U joints and also the main drive shaft u joints

Any odd noises or pulling to one side or the other?

tnsg

It does have after market wheels, I will check on original equipment sizes. Tires have been replaced.
I have not checked wheel bearing, but there is not any noise.
What is rear 1/2 shaft U joints? how do you check U Joints? see if they are sloppy or have play in them?
There is no pulling to one side or other.
When it does do it, it feels evenly over the whole car.
I have limited mechanical experience.
Thank you for responding

81c3

Ok, if the wheels are aftermarket and not quality, that could be the issue... Lots of Chinese made offerings out there... some are not as good as others... Sometimes its impossible to get them to balance out.
1/2 shaft is a small drive shaft with U joints on either end. This is what drives your rear wheels on your independent rear suspension. Generally the way to check them is to move the drive shaft up and down and side to side. There should be no play. The 1/2 shafts look just like the main drive shaft only shorter. Allot of times bad U joints will make some noise, but not always.
No pulling is good, that minimizes an alignment issue.
The way to check wheel bearings is to jack the car up a few inches off the ground. Take a pry bar and see if you can pry up at the 6 O clock position... there should be no movement. Then grab the tire with both hands, P & 3 O Clock position... try to move side to side, there should be no play.

tnsg

Thank you so much. Some valuable information. I will check on wheels, they do have the corvette symbol, but that may not mean they are American made. I will try to check U joints but I do not have a lift. I will check wheel bearings that looks straight forward. We watch grand children a couple days a week so it may take me a few days. But I will keep you posted.
Thanks again, I would really like to get it resolved so I can enjoy the ride.

MatthewMiller

Yeah, this is all good advice, and exactly what I was thinking as I read your description of the problem. If it were tires or wheels, I'd expect the problem to always be there. I'd really look at the two halfshafts: in addition to driving the rear wheels, they also serve as the upper lateral suspension links. If one of the U-joints is dying, it could vibrate and cause some noises. It can also affect alignment intermittently. A tell-tale sign is if the car slightly changes direction when you transition from on-throttle to off-throttle.

I would also check the two U-joints in the main driveshaft. If you're getting noise and rumbling vibrations but no steering changes, one of them could be dying. Wheel bearings are a possibility, but I kind of doubt you'd get that kind of severe rumble from them. OTOH, if the rumbling goes away with brake application, it might be the bearings.

BTW, one way to narrow this down to front or rear: if the rumbling is more felt through the steering wheel, it's in the front end; if it's felt more in the seat of your pants then it's rear or the main driveshaft. Good luck with this! Let us know what it turns out to be.

tnsg

Matthew, Thankyou for your response. The most difficult thing to find the problem, is that it does not do it all the time, in fact sometimes if you go for a short drive it doesn't do it. Next time it may do it after driving for several miles. I will follow-up on your suggestions. I recall that I feel it in the steering wheel but I will take it out again and check on that issue, good advice.
Thankyou again,
Tom

KurtK

Sounds somewhat similar to the problem I encountered a few years ago.
Turned out some of the rear bushings were shot.

The shop replaced the the bushings for the leaf spring, control arms, and strut roads.

tnsg

Thank you, this is new information. Did you experience the problem at various times or was it an issue whenever you drove it? Can you physically see if bushing are bad by visual inspection?

KurtK

The severity of the vibration was more noticeable at higher speeds while turning- such as the road curving. I first noticed the problem while on a freeway on ramp that curved- possibly due to loading the suspension.
Straight line driving was OK. Low speed driving was OK.

radar502

The control arm Bushing test , Jack up till the wheel is off the ground 3 or4 " slid big bar under the wheel a few inches lift up on wheel need to put some back in to it have someone looking at the control arm for movement you might be able to feel it moving do at 4 Connors .. Just a fast way to check if rely bad bushing ..and you might not be able to see if a bushing is bad or by looking may be broken down in the sleeve and you really can't tell ,all cracked up needs to be replaced .. Sounds like a bushing .. and at first they come and go until they just fall apart ( Flat bed) not driving home .. If stock C-4 I say about all the bushing if not bad dry rotted anyway time for a refresh .. most are 15-20 years old heck mine is 26 years old had to replace most all the bushings ..

tnsg

My issue has always been straight line driving usually on the interstate at 60 to 65 mph it will just start vibrating to a point that is very uncomfortable, doesn't always do it.
Ok so today I thought I would take it out and see if there seems to be any pattern to it. I noticed that there is a very slight vibration in the steering wheel at all times, I drove approximately 25 miles and nothing happened. Got off the interstate and turned around and got back on and it started to vibrate increasing until it seems unsafe, I accelerating till about 70mph and it continued to get worse, applying the brakes also did not stop it. Pulled off to a total stop and started out again and it was ok. Any thoughts?
Thank you

tnsg

Thank you, it does make sense that the age may require bushings. I think this is probably something I would have to have a shop replace them. Do you thing the description of my experience today as below would likely be the bushings?

My issue has always been straight line driving usually on the interstate at 60 to 65 mph it will just start vibrating to a point that is very uncomfortable, doesn't always do it.
Ok so today I thought I would take it out and see if there seems to be any pattern to it. I noticed that there is a very slight vibration in the steering wheel at all times, I drove approximately 25 miles and nothing happened. Got off the interstate and turned around and got back on and it started to vibrate increasing until it seems unsafe, I accelerating till about 70mph and it continued to get worse, applying the brakes also did not stop it. Pulled off to a total stop and started out again and it was ok. Any thoughts?
Thank you

81c3

Does sound like wheel/tire balance still to me.... Try having the wheels/tires Road Forced Balanced. Big O shops usually have the machine.

novaks47

Sounds like something is binding and then resetting. Does the vibration feel like it's coming from the front or the rear? If it's the front, it could be a tie rod end binding up. If it was a balance issue, it should be happening all the time.

MatthewMiller

The small vibration in the steering wheel is probably just tire balance. If the big vibration that comes and goes is not in the steering, then we're back to driveline, most likely. Bushings don't cause this kind of thing. I forgot to mention the rear toe links. These are the same concept as the tie rods up front, except they just mount to a stationary bracket at the diff. Make sure they don't have play in them. That could do a number on your ride quality if one tire is wobbling around in toe. Also, make sure all your rear suspension links are bolted tightly. The camber eccentrics and their brackets in particular have a bad habit of coming loose.

CorvetteRules

My 91 starts vibrating once it hits about 70 and the first thing that came to mind was a balancing issue. Below 70 it rides smooth. I haven't tested my theory by having tires rebalanced yet, but if you have your tires balanced and problem is solved please report back to us.

RedRedRed

Have you had any luck diagnosing this? My recently-purchased '91 is doing exactly the same thing, intermittent aspect and all. I thought it was flat-spotted tires since it's only got 13K miles on it and the tires were 13 years old. I think the car sat in a collection a lot. I drove it home to my townhouse from my place with my shop and my lift and had new tires put on. Still does it. Now I'm not too sure I want to drive it the 120 miles back to my other place to get it up on my lift and have a look. I may want to take it somewhere and have it checked out first.

If you've gotten any where with it, I'd love to know what you've learned.