chrisz

Hi all,

Our 2005 with about 50K miles has had an odd vibration only noticeable within a certain speed range, noticed at 40 mph +/- 3 mph. Initially we thought it was an uneven road surface, but then started paying attention. Then started noting that we could feel the vibration when ever we hit a certain speed range (40 mph). The vibrations are fairly high frequency, no noise is heard. Before we hit 40 mph the car ride is smooth, and after about 43 mph its smooth again. Does not matter if the car is in gear or not. The tires are 6 month old, but the vibe was there with the old rubber as well. The car tracks well, the engine runs well, no issues shifting, no rattle in the clutch. When the tires were installed we also had Honda do an alignment. We haven't tried swapping the wheels (they are not damaged) from side to side to see if there is a difference. The bearings feel fine (car lifted) to try to move the wheels by hand, up/down and side/side.

I think there is a resonant frequency that is being excited at that particular speed, but trying to diagnose where it may be coming from is a bit frustrating. Tried searching this forum and while there are many topics regarding vibration, didn't manage to find one that would occur at certain speed.

Hoping someone might have an idea where to look,
Thanks in advance.

windhund116

Sounds like a tire imbalance issue. Maybe have the wheels/tires dynamically balanced?

dsthez

That's a tough one. If a rim is bent maybe you can buy or try on a stock ap1 set of wheels or something like that. But at the same time wheel balance issues are usually felt around 65-70 mph... where is the vibration front rear left or right?

chrisz

If it was tire related, I would expect it to get progressively worse as the speed went up. But as the vibration goes away at around 45 mph I don't think it is tire related.

Car Analogy

Its unlikely to be tire related, as OP stated in first post that issue was present even with the old tires. Its possible its a wheel, as OP considered. But rather than swapping them side to side, as OP thought he might try, I would try to find another S owner to temp swap wheels, and see if issue remains.

I agree its a resonant, harmonic thing going on. What happens if you coast down through below 40 from like 60? Does it still happen? Try it in gear, try it in neutral. Report back findings.

jyeung528

check the prop shaft balancing. also, the diff pinion gear flange nut could be loose.

Slowcrash_101

Prop shaft imbalance manifests itself around 70 mph, 40 mph and goes away sounds like differential mounts.

dsthez

I have no further ideas let us know if you figure it out man..

roadsterred

Have you done a Google search on Honda S2000 driveshaft vibration?