DNF Dave

I'd like to add my own problem to this thread, as it sounds similar to the problem Kenny's having.

My stock 2003 S2000 has been developing a worsening shake/vibration over the past 5 driving days, and it's starting to get really bad. Car has 21,000 miles. All fluids are good. No leaks or damaged seals noticed. All tires recently rebalanced, which had no effect on the problem. The exhaust is not rubbing or vibrating against anything.

During acceleration, the car shakes/vibrates, especially over 3500RPM to 6000RPM+, and especially at speeds over 40MPH. Shaking is the same in all gears, and increases with RPM. When I press in the clutch and rev the engine, there is no vibration. When I'm flying down the highway and am not accelerating, there is no vibration. Only when accelerating while in gear.

It's very hard to tell for certain, but it feels like it's engine speed sync'd, but I just can't tell for certain (darn those close ratio gears!). I haven't overreved the engine. I don't notice any clutch problems. no slipage, no shifting problems, except I've always had moments when the depressing of the clutch doesn't always allow for smooth shifting out of gear, and it feels a little stuck. Usually releasing and re-depressing of the clutch resolves this occassional stiffness. Since the vibration has developed, shifting performace feels the same as it always has.

If I had to guess, I'd say it's the rear end, or a bearing, or a flywheel or tranny gear with a broken tooth, but I'm just guessing (and I'm very prone to being wrong).

I came across other threads here on S2KI.com that had similarities that recommended smacking the MAP sensor, but I haven't been able to try this. The car is now now at San Francisco Honda, and they don't yet know what the problem may be. They are currently blaming my 245/45/16 tires, blaming the non-OEM size tires for causing a problem with the limited slip differential, and the service advisor is telling me that there are error codes being generated that are coming from the Limited Slip Differential indicating a problem due to the size difference front to rear. When pressed to explain, he backed off this diagnosis, but told me he wanted me to switch back to OEM 225/50/16 tires, which I'm not wanting to do as my 245/45/16 are the size that TireRack, and everyone else who seems to really know, recommends, and my current tires are still in fantastic shape.

Any help here would be greatly appreciated. Anybody in the San Francisco Bay area that knows anyone knowledgable about S2000 drivetrain problems, or can recommend a good dealership mechanic, I'd appreciate the advice.

Thanks! - David Ness

xviper

Dave, I would suggest you find a more knowledgeable dealer. There are NO sensors in the rear diff that would confuse the ECU and throw a code, so this part is As for the 245 tires, these ARE the correct size for the rear in a non-OEM tire. This is common knowledge and the fact that your dealer does not know this makes them a poor choice. This issue has been discussed at length here:
https://www.s2ki.com/forums/index.php?showtopic=48572

I suppose it wouldn't hurt to do the "MAP whack" and ECU reset, however, I somehow doubt this will resolve your situation. It would seem that your condition is associated with a given engine load. This could be anything ranging from something in the engine, to the mounts, to the prop shaft, to the rear diff, to the CVs, to the hubs. Most of these things can be inspected and some tests performed to take them out of the equation. An experienced mechanic (not necessarily a Honda one) should be able to check this stuff out.

Another possibility: Some owners are super sensitive to things that they perceive as unusual shaking and vibration. I went for a test drive with another owner who was indicating that his car has an odd resonating noise that he could hear. When I rode in his car, it was simply the normal noise that the tires make when the noise bounced back off adjacent objects. This could be you case. Have another S2000 owner go with you and see if the condition seems odd to them.

mikegarrison

Well, as I read your account I suspected your diff before you mentioned it. From your statement about no vibration when the car was in neutral or not accelerating, it seems like a thrust-related problem. I suppose that could be anywhere in the driveline, but the diff seems most likely to be sensitive to thrust issues.

However, as long as your tires are the same on both sides the diameter of them should make no difference. Your dealership is either really clueless or desperately searching for something that they can claim is your fault.

I would say the diff should be at least opened and inspected.

BTW, now that I reread the original post he also says that it is thrust-related, not strictly RPM related. I missed that detail the first time around. It sounds like you both have the same problem.

DNF Dave

PS From David:

Thanks for the responses. I appreciate everyone's insight and experience. Keep it coming.

I just wanted to add that I've never had a check engine light come on, and don't believe I've seen a decrease in power, although I have to drive more gingerly due to the fear due to the significant vibration. The vibration certainly started out being subtle, but is now so significant that anybody would know that something is wrong. Also, I've never changed the plugs, had the valves adjusted, or anything else except Mobile 1 & Honda Oil Filters every 3500 miles, and I run a K&N air filter, although I've switched back to OEM while it's at the dealership.

KenGPW

OK last night I went for a long drive so I could see what RPM the shaking started to happen at. I can accelerate with very little throttle without almost any vibration all the way to the RPM range. If I lean into the throttle 50% or greater, above 4000 RPM the vibrations start. As soon as I hit Vtec the shaking gets very bad all the way up to 8000 RPM's.
Just from the way it feels I am almost certain that it is my Diff. I can cruise at 7000 RPM steady with no vibrations at all. Touch the gas to accelerate, and it vibrates/shakes so bad it is pretty scary.......

DNF Dave

With regard to my car (the second one mentioned in this thread)...

In the end, I paid to have a stock set of rear tires mounted to my car so the dealer (San Francisco Honda) could see that this wasn't the problem, which I had been telling them. So now it's proven, and they were forced to look deeper for a problem.

Now they say they are 95% sure it's the rear differential, and are going to replace it with a new one under warranty. It'll take a few days to get it in and install it. I'll be certain to post a follow up to this thread.

- David

mikegarrison

Yeah, from 1000 miles away I am 95% sure it is the rear diff. Please ask them to open it up and let you see what is wrong. That would be good info for the rest of us.

xviper

Welcome the world on online diagnostics.

WtbS2k

jcurtis

I would recommend checking the CV's as well. My car has a similar issue and My guess is that it is the CV's.

Jeremy