1994 - shakes when I reach 68-74 MPH

[Shirley Merle]

Lately I have noticed that my vette starts to shake violently when driving down the freeway. Its starts when I reach 68-74 mph. Can anyone tell me why this is happening before I take it to my local mechanic? I have considered that it is being caused by the freeway itself. (I live in L.A. and work in the Ventura County region). I have also had my tires rotated and balanaced thinking that this might be the problem. It did not fix it.

[94conv.]

When you had the tires balanced, did they check your alignment? How old are the tires, could posibly be a broken belt in the tire but I think you would notice wandering in the steering and evening a bounce or thumping during normal driving at any speed, at least above 30mph. Have you checked the bearings by grabbing the top of the tire and trying to rock it to check for play? Outside of a drive shaft or half shaft being out of balance those are the only obvious things I can think of to check and with one of the shafts, I dont think its something you would just now notice. Good luck with it and keep us posted. Does it feel like the engine is cutting out or missing out at all or do you notice the transmission trying to shift back and forth or anything like that?

[Shirley Merle]

I would say they are about 4 years old. I bought her in 2002 and have not had the tires changed out. She had 24K on her at that time and now has about 46K. No, the engine isn't cutting out or missing. I had noticed about 4 months ago, when I was at a stop light, the engine would shift back and forth. So I took it to my mechanic, he put her on the analyzer and all, but nothing. Put about a grand worth of work into her at that time (the usual periodic maintenance). She did it for a little while after that, but I haven't noticed it in a few months. I really noticed the shaking (a lot more than normal, really scared me) this morning on my way to work. But the shaking has been going on now for about 6 months. That is why I took it in to have the tires checked out, rotated and balanced. Will try what you noted above.

[Shirley Merle]

I also don't have the wandering you mentioned above, I have noted that the steering wheel while driving straight is right on center. There is no thumping or bouncing sounds either.

[74bigblock]

Drive shaft threw a weight? Could be unbalanced and at that speed and RPM, it is setting up a reverberation.

[Shirley Merle]

Thankyou 74bigblock. After your reply, I spoke with my mechanic about what you said and also 94corv suggestions. I hope that it solves the problem. Will be taking her in over the holiday. In the mean time, I will drive her home (no led footing) and put her to bed in the garage.

[vee93]

Lately I have noticed that my vette starts to shake violently when driving down the freeway. Its starts when I reach 68-74 mph. Can anyone tell me why this is happening before I take it to my local mechanic? I have considered that it is being caused by the freeway itself. (I live in L.A. and work in the Ventura County region). I have also had my tires rotated and balanaced thinking that this might be the problem. It did not fix it.

Before you get charged for a diagnostic fee (aka-tech labor $$$ for looking..er..., checking), wheel alignment, balance, etc..., do one simple thing--please just go and check the air psi in all of 4 of your tires.

[94conv.]

Good call 93. I thought I had an alignment problem once and thats what it was.

[John Robinson]

Have you hit any craters recently that could have bent a rim. I had to have a rim straightened to make my car run smooth


You said that you had the tires rotated. I am not sure how you can do that since the tires are specific as to which direction they rotate. Also the rims are directional. If you had a tire that was scalloped out because of low pressure etc, it would create a vibration if it was switched from side to side. With the mileage you say the car has I would be more suspicious that your problem will be in the tires or rims. Good luck and let us know how it turns out.

[Baldie88]

Try pulling your wheels off and check the insides. I had a similar problem and even after rebalancing them I still had a vibration. A long time Corvette friend suggested cleaning the back sides of the wheels. The had a thick build up of brake dust and grease even though the outside was spotless. Scrubbed the backside down real good and have had no more vibration. I'd try this first since it's the cheapest and if that doesn't cure it then I'd go with your other recommendations concerning bent rim and/or alignment.

Good luck.

Ron
"Baldie88"

[HD2HVETTE]

Alignment itself does not cause a vibration, bur will cause uneven tire wear resulting in a vibration. Hard to see the inside edges of your tires, but try running your hands over the tread surface. If any of them feel uneven (bumpy) that is likely your problem. Does the vibration continue above 74 mph or go away? If it goes away it is not likely to be your driveshaft, but tire related.

[74bigblock]

You could also have a broken belt in a tire... but this should cause a vibration at all speeds, and get worse as you go faster. Just another thought.

[ßill]

I didn’t see anyone say anything about “U” joints. A worn “U” joint may allow the shaft to whip around causing a vibration. Remember we have 6 “U” joints in our “IRS” Vettes. I have had this problem in both of my ‘90’s in the last year. The “U” joint problem is usually associated with a clicking noise.
Good Luck

[Hrtbeat1]

You don't say which transmission you have, but it could be the torque converter locking and unlocking. Is the vibration constant, or does it come on at partial throttle? Does changing the throttle position change the vibration, increase/decrease? Does it do this just on the freeway, or on other roads?

[compyelc4]

Do you have the Low Tire Pressure System (LWPS) option? The reason I ask is I nursed the same problem for one summer before I found out that some idiot broke a sensor strap on the driver rear wheel when he patched the tire for the previous owner. For some strange reason the tire would not "go out" until above 60 mph. Below that it was fine.

Crazy thing is before I found the problem I had the tires balances numerous times. Each time the dealer would say the wheel balanced up just fine, mount it, and I'd be on my way. Problem was, as soon as he removed the wheel from the machine and mounted it on my car the weight would shift around inside the tire and become immediately unbalanced. Of course the dealer would just scratch his head (I'm being kind) and wonder what he did wrong. The final dealer I went to told me to get new tires; that the existing ones could not be balanced. I just had him remove the other three sensors and straps. Voila! Man was that guy embarassed.