My 2005 has about 30 hours of racetrack and 85,000 miles of commuting with no mechanical failures. Only S2000 owners say things like that! For the first 10 hours or so of track days i ran the car with the same wrong diff fluid Honda gave to all of us but after long days at the track i heard some pretty sad sounding noises comming from the hot rear end. I changed to an R-Compound (LE) fluid and the post session noises went away. So years later, in the last month or so i get this vibration the first block or so i drove and then it would go away. Now the vibration doesnt go away so i started pulling and prying on chassis stuff but everything felt tight. I replaced all my hammered tires, which i needed anyway, but it still vibrated. So i get back under the car looking for loose bushings and ball joints i previously missed and noticed the axels have appropriate axial (in and out) play, almost none, but a whole mess of radial play (up, down, all around)at the differential. All the exposed bolts are tight but the diff flange is loopy inside the housing. So im going to start inspecting and tearing stuff appart saturday morning hopeing for somthing loose and not somthing totaly wiped out. I cant hear anything wrong when driving so hopefuly its not that bad yet. Ill consider inner joint wear spots on a lowered car and rotate the cups but its been 40,000 miles since i lowered the car with no vibration until now. Im not in a hurry to take the rear end appart either, ill do some better inspection first.

I was hopeing to hear someone else had the same problem and could tell me what im getting myself into or what to expect parts replacement wise. Im a formally trained, but green, auto tech who hasnt had a diff appart since school, not that im worried.

 

A little axle play is normal. Is the vibration under acceleration only?

 

Its the same under braking and acceleration, clutch in clutch out, gets worse with speed, vibrates at the frequencey of the wheels rotation with no change in vibration from driver imput. Its like an out of ballance tire really. The car doesnt surge either which is odd. I figure if somthing was wrong with the diff it would cause some resistance in the drive line feeling like pulsing deceleration but the problem is very neutral, like a bad tire, but occured with two different sets of tires.

 

pitted cv buckets?

 

Ill have to see nick, but the car operated fine at Homstead last month with you guys.

 

Does not sound like worn CV buckets (that's what I was getting at too) even though the vibration from that can start suddenly (feels fine one week, shaky the next). You should mainly able to feel it under acceleration, and worse when cornering. It should dissapate to next to nothing under steady throttle and dissapear under no throttle.





One side of each lobe is contacted with throttle input on forward gears.. you can see how it would wear over time

 

Seems this issue is becoming more common. No one has been able to figure it out yet.

https://www.s2ki.com/s2000/topic/100...#entry22365468

In there, there's a link to yet another even longer running thread with a bunch of failed attempts at what might be causing it. The only sure fire way to cure it seems to be hard top (oddly enough... maybe air flow over the top is the cause? maybe lack of rigidity?).

 

I pulled appart the rear corners and swapped the axel buckets. They looked like 20,000 miles, nearly new . I also played with my damper adjustmment and the feeling of vibration gets less noticable the softer the dampers so i figure they are not blown.







Also, next time anyone has their car in the air check for this level of play on a smooth driving car.


http://static.photobucket.com/player...ps5618e886.mp4

Im going to go over the front now and also look at motor mounts eventhough it feels like its in the rear.

 

are the rear diff mounts leaking?

 

i didnt know they were hydraulic. the diff mounts are in good shape. at one point i supported the car by the diff case and mounts looked to be in good shape. every thing was clean and dry around the diff area.