i had a vibration at 72-76 mph (in any gear, accel/decel/coast) and i have determined that the previous owner changed clutch and replaced 1 of the m10x1.25x62mm driveshaft bolts with an m10x1.25x60mm bolt. If i switch the bolt positions around, it changes the vibration behavior. runs thru rpms smooth like butta when i take off drive shaft. I just went and bought 12x 90182-s2a-a00 bolts from honda. my assumption is that these are hardened grade 10.9 or better (sae grade 8 or better) and corrosion resistant, so you dont want to replace with non-oem. black oxide hardened bolts will mess yo shittup. also, make sure you get the late model year bolts, since the have an 8mm hex drive instead of the 6mm hex drive i think early models had (not sure). torque spec is 24 ft lbs. i use hex bits with 3/8" drive, a 6 incvh wobble extension, and a 3/8" drive torque wrench to change them.

FYI, this happened after i changed clutch and wheels/tires, so i first thought it was the new wheels/tires, but did troubleshooting to determine it wasnt (still vibrated on jack stands with no wheels on at 72-76 mph). THANK GAWD IT'S NOT THE FLYWHEEL which is ap1 resurfaced.
My car is 08 s2000 berlina black with kraftwerks kit and 65k miles. Running act pp/oem everything else with ap1 fw, and ap1 slave cylinder.

Also, good luck finding a shop that can balance a cv shaft. Everybody does only u joints shafts. I had a few places offer to convert me to cv for like $700, but i will stick with honda engineering (science) over some guy at the driveshaft shop's opinion; he probably works mostly with semi trucks anyways.

 

When I had replaced my differential, and later on my clutch, I replaced the factory driveshaft bolts with grade 10 bolts and locking washers from my work. No vibrations and they're definitely reusable. I'd recommend doing this.

 

Wait, I have the same issue! Could this be what I've been looking for all along? lol

For reference you are referring to the bolts supplied with driveshaft spacers correct?

 

That would be correct.

 

It makes sense if bolts are all the same, even if not factory parts, they're balanced. Whereas if they are mismatched parts, its easy to imagine they don't weigh exactly the same.

But I have a hard time imagining the minute difference in one bolt vs another of roughly same size is enough to cause annoying vibrations. But I certainly could be wrong.

 

Awesome, thanks man! Did you torque them to the factory 61ftlbs?