I have a 2002 Z06 with 42k. At 70mph and higher it has a consistent on/off vibration, about once per second. Others have described it as “cyclical” or “pulsing.”

PLEASE do not suggest tire balancing. It is not the wheels, tires, or brakes.

I just got it back from a Corvette specialty shop and they have not been able to diagnose, but we have eliminated many culprits.

The source is definitely in the rear. It is speed dependent, does not matter RPM or gear.

It is not the torque tube or harmonic balancer.

Shop says wheel bearings and half shafts are fine.

Changed diff fluid, they said it was clear.

Changed transmission fluid, it was murky brownish red. Strainer picked up tiny non-magnetic metal pieces. Shop said fluid looked like 90k, not 40k.

Shop suspects transmission output shaft/bearing, but I didn’t have them open anything up.

I have read many threads describing similar symptoms, but have not found any conclusions.

 

You've got me stumped, but it is obviously in the drive line.
You've come to the right place for help, I just wish I could.
Hopefully someone on here will have the right answer.

 

I had a vibrating problem in the front wheels at about 70 to 100 mph. Balance 3 times,. Changed front tires. Bearing felt great. Had me stumped. I had a guy on this forum suggesting possible front wheel bearing which I didn't take serious due to them feeling so good. Then a bearing started making noise in the rear and I just went ahead and order 4 bearings and changed them out. Surprise surprise surprise. Front end vibes went away. Check for them from 79 to 140 and all smooth. That was about 25 K miles ago and still all good.

 

Moved to C5 Tech.

 

I cannot help directly, but I can throw some more information at the problem. I have a 2003 that does the same thing around 70mph. It is a subtle, rhythmic vibration that comes and goes around 1 second intervals. The car is an automatic with 3:15 gears. Less than 3000 miles on it, but fluids are changed at yearly intervals. Tranny fluid changed once, about a year ago. Tires are 2 years old and road force balanced. Car is run on regular basis.

I doubt that there is enough wear on my car to cause the vibration.

 

Are you feeling the vibration in the steering wheel?

If you find a shop that has a pico NVH diagnostic capability, they should be able to isolate. One possibility is the rear diff mount. Just like a bad engine mount can cause unusual vibrations, so can that mount. There are 2 nuts that hold the mount to the cradle. Check them for being loose.Another is something internal to the diff, since it is wheel speed dependent, and not rpm dependent. Of course trans shaft bearings could be the problem. but they will tend to whine all the time.

 

I feel it in the steering wheel, but I doubt a passenger would feel it. I chocked it up to the road surface, combined with the speed and tires, causing a rhythmic vibration. Much like the rhythmic vibration the old multi engine prop planes would have while cruising. Reading about others having similar symptoms makes me wonder.

 

It might be the ring gear on the differential. I had a cyclical vibration noticeable mostly at hwy speed. See the picture....

 

Part of the diagnosis was running the car on a dyno so the technicians could look for any obvious loose or out of balance parts while at speed and vibrating.

This confirms whatever is happening is coming from the rear since the front tires weren’t spinning.

That said, while the source is in the rear, the sound and feeling of the vibration shifts from rear to front and back while driving occasionally. I have not determined how to create the shift intentionally.

Mostly I feel it in the seat and hear it behind me, but suddenly will hear it in the front of the car and feel the pulsing through the steering wheel.

I’m assuming this means whatever is causing it is sending harmonics through the drivetrain up to the front.

 

Well vibration frequencies in the audible range will make the passenger compartment a sound chamber, so no surprise you are feeling it. Especially a FRC or Z. One of those foam trunk barriers will make a big difference on heard and possibly felt vibrations.

Tire vibrations can be brand- specific, and summer tires in cold weather will have flat spots that take a lot of warm up to make go away.

Your car can handle a lot more camber than you might think, as long as you keep the toe settings very close to zero (not just GREEN on the alignment readout sheet, ....ZERO). You can usually go to 0.8 camber front and rear. That will change the tire contact patch shape a good bit, and will reduce some tire noise and tram lining. The Goodyear original run-flats weren’t a great tire. There are lots of better choices these days.


There is a vibration damping weight bolted to the left side of the diff. Check the securing bolts to make sure they are tight.

 

There have been numerous similar posts over the years and there is rarely a direct answer...I know this because I have searched for the same issue before many times lol. A rhythmic, cycling, subtle vibration that can be felt through the steering wheel at highway speeds and seems like it kind of "rolls" through the car. The odd part for me is that it's not 100% consistent. Some days it will do it very noticeably and others I swear it doesn't do it at all. Definitely not a wheel balance issue as it did the same thing on 2 out of 3 sets of wheels I've ran on the car.

I'm in the middle of replacing all hubs, ball joints, and tie rods and will be happy to report back if the problem persists or remains. I can tell you that, at 50k miles, my lower ball joints all seemed good still, but most of my uppers were loosey goosey and the front tie rod ends weren't too far behind. Having completely disassembled my entire suspension now, my best guess at this point is either an upper ball joint, front tie rod end, or a hub/bearing will be the culprit.

 

Was really hoping it would be something this simple. Unfortunately good and tight, but worth checking.

 

I once had a problem exactly like this. In the end it turned out to be the transmission output shaft bushing was worn. It caused the driveshaft to waller around and be inconsistent in when it happened. When it did, it was cyclical just like you describe.

 

I have a 2014 C7 with the 6 speed automatic transmission with 10,500 miles on it.
I have just noticed this surging/cyclical vibration which seems to start at 60 MPH and is more noticeable cruising on the highway above 70 MPH.
The vibration is not in the steering wheel.
The car is not driven regularly, but the tires are not flat spotted.
I took the car to a local Corvette Center and they balanced all 4 Michelin Run Flat tires. 3 of the 4 tires were out of balance 1/2 to 1 ounce.
The Corvette center said that with so low miles, that should solve the vibration issue, but they didn't road test it like I asked them to do.
On the highway drive home, the vibration is still there, so I called the Corvette center back to tell them.
They said that the front tires do have some wear on their inside edges and since the tires were made in 2013, the next thing to do would be to replace the front tires, re-balance the wheels and align the car.
The Corvette center said that the rear tires, also made in 2013 still looked good, so they didn't need to be replaced.
As all 4 tires are 7+ years old, I'm thinking of replacing them anyway due to age and getting them balanced and the alignment done, so we can definitely rule out the tires and wheels.
I personally don't think it's the tires, but the Corvette Center said that we need to start there before they start looking into the drive train, which could get expensive.
I was hoping that as they only work on Corvettes, the Corvette center could better pin point the cause.
Any comments regarding my situation are welcome.

 

At 8+ years old, I'd definitely replace the tires due to age alone. General rule of thumb is 6 years I believe. Some people will say they have no issue running 10+ year old tires, but most will agree that's flirting with disaster. I did have a 10+ year old tire delaminate on my Jeep a few years ago, luckily I was only going about 30 mph.

Did they check for play in the ball joints and hub? Balancing a tire is always the easiest/cheapest thing to start with, but I don't know why they wouldn't also check for suspension component play with the wheels off the ground already.

 

The Corvette Center didn't check anything else.
When I take it back to them to change all 4 tires, I'm going to make sure they take it on the highway up to 70 and if the vibration is still there, then they can tell me what else they will check.
I just hope this doesn't cost me an arm and a leg for such a low mileage car.
Thanks for your reply and I'll let you know how things go in a few weeks.

 

RESOLUTION!

I replaced both rear hubs and the vibration is gone! So much more enjoyable now.

Hope this helps some folks in the future and thank you everyone for your responses.

Enjoy this pic from my celebration drive through Rocky Mountain National Park.

 

My issue seems to be resolved as well. If hubs are the/a solution, it wouldn't hurt to replace the ball joints and tie rods while you have it all apart. I went the whole nine yards at all 4 corners plus coilovers. Feels like a new(er) car! lol

 

wheel bearings will do that

 

I’m going to lower it and have an alignment done, see if they think anything is wearing out. It feels just a little bit squirrelly sometimes.