My car (31k miles) has a problem with shaking/vibrating at speeds over 70 mph. I'm aware of the issues concerning CV joints, and my car's symptoms don't quite match up - there is no clicking and the shaking will occur while driving at a constant speed on smooth pavement. Unlike cars with CV joint issues, turns and acceleration do not cause the symptoms.

The shaking/vibrations occur at speeds over 70 mph and are particularly strong at 75-80 mph. I haven't gone faster than 85 mph since the symptoms started. The shaking comes and goes in pulses and isn't consistently associated with turning, acceleration or deceleration. It seems to be coming from the rear of the car with no shaking being transmitted through the steering wheel. When the shaking occurs it does not change in intensity or frequency when the clutch is pushed in or if the car is placed in neutral with the clutch either in or out.

After road tests with the S2000 tech and the shop foreman at a local Honda dealer, the consensus was that the wheels were out of balance (Bridgestone RE 740 tires mounted on OEM rims). The entire set had recently been high-speed balanced at their shop the previous month. The shop foreman said that the symptoms were consistent with water or fix-a-flat in the tire so the rear wheels were dismounted, the tires were reset on the rims and the wheels were rebalanced. There was no foreign material in the tires and the shaking remained. I do not think this is a balance issue because the shaking occurs when using a completely different set of wheels (Kumho V700 tires mounted on OEM rims). The only commonality between the two wheelsets is that they were both balanced at the dealership.

At the request on the dealer, I am having the wheels balanced using a high speed balance machine that works when the wheels are mounted on the car. If that does not fix the problem, the next step is to investigate problems with the drive-line.

Any insights? Thoughts? WAGs ?

 

I think your on the right track. I would check the drive shaft.
Do you feel while holding the gear shifter?

 

If you keep adding speed does the vibration go away at some point?
Does the car actually shake, or do you just hear the vibration?


first train of thought: How is your alignment? A poor alignment can cause vibrations like this that don't appear until you hit a certain speed, reach a peak at a certain speed and then disappear once you pass that speed of maximum vibration.
second train of thought: Symptoms suggest to me that you possibly have a loose mount for something somewhere that is causing a harmonic resonance.

 

The shaking is mostly felt through the seat of the car. The pulses are occasionally strong enough to rattle your teeth and cause other rattles in the passenger compartment. The shifter vibrates, but not moreso than other S2000s I've driven/ridden in. If you hold the shifter, it doesn't shake with the same frequency as the car.

The car was driven up to 90 mph by the chief diagnostics mechanic at Lexus. The shaking remained consistent up to about 85 mph and then seemed to diminish at 90, but we were only there for a short period. At Lexus, the rear wheels were rebalanced on their high speed balance machine and then "finish balanced" by a machine that balances the wheels when they are mounted on the car. The technician could not get a consistent finish balance on the right rear, but could on the left rear. He thinks the problem is in the drivetrain somewhere. The car goes "under the knife" at Honda over the weekend, and I'll report back after the Honda techs have had a whack at it.

It's been a most perplexing problem .

 

honestly, I'd check the alignment before shelling out for mechanics.

 

I had a similar (but less severe) problem years ago that was solved by the 'mounted balance' which helped me find the problem. It was the wheel locks that weighed three times what the regular lug nuts weighed.

This problem sounds more serious, and since you have eliminated wheels and tires themselves as the problem you have to look at the mounting and then the other rotating mass. IMO the balance will only mask the problem.

 

The Unabageler - The car was aligned a few months ago and the two techs that I talked with about the problem never suggested alignment as a possible cause for the shaking. I'd think that mis-alignment would show in handling and tire wear issues, not vibration and shaking, especially from the rear.

cdelena - I do not use locking lugnuts on the car, so that's not it. The problem remains despite the multiple stabs at balancing using some pretty nifty equipment.

On a few occasions I've noticed a loud clunk coming from the back of the car. It is not reproducible, but once occurred when I was turning left and the suspansion bounced over a speed bump. It occurred another time when turning left over rough pavement.

Thanks to all for their suggestions - I'll follow up after the weekend with results.

 

I only suggest it b/c that's how i fixed shaking/vibration probs on my oldsmobile and the gf's mustang. just my $.02

good luck w/ this!

 

Have you tried balancing the front wheels?

 

any more news on this? I'm looking forward to hearing what the problem is/what fixes it!