Vibration @2k after clutch/LWFW/mounts

[xer0trigger]

Hi all,

The preface: My TO bearing disintegrated on me, so I decided to do a drivetrain overhaul. I've replaced all the tranny seals, the rear main seal, pilot bearing, etc. New Sachs clutch and PP, TO bearing, clutch fork, etc... Had the flywheel lightened and resurfaced (now 13lbs. down from 18lbs.). IE urethane motor and tranny mounts. New guibo and CSB.

The problem: In gear or out, clutch in or out, sitting still or driving, I get drivetrain vibrations most noticeable between about 2000-2300 rpms. It's kind of a "lump-lump-lump" feeling like a wheel out of balance would be, but in the drivetrain (for lack of a better description). Anything lower or higher in the rpm range than that and it's pretty much unnoticable.

My question is - should I be worried? Is this normal on new clutch installs that will fade with use? Or perhaps I'm just feeling the added NVH of my lightened flywheel and urethane mounts? Or is it symtomatic of something more serious like an out of balance flywheel?

TIA

[jlevie]

Was the rubber mount of the CSB torn? If so I'd say that the vibration is from binding u-joints in the drive shaft, which is almost always the cause of a CSB failure. The fix is a new or rebuilt drive shaft.

[xer0trigger]

No, CSB wasn't torn, just some slight fraying of the rubber around the edge but I figured I'd replace it while I had the driveshaft out. I wouldn't think it has anything to do with the driveshaft however, considering the vibrations happen when the car is out of gear and not moving - which would mean the driveshaft isn't spinning at all.

[jlevie]

If you have vibrations with the car stationary, the motor/transmission mounts are to blame. Poly motor and transmission mounts are a lot stiffer than the OE mounts and will couple vibrations into the cabin.

[xer0trigger]

I hope that's the case. I expected added vibration from the lightened flywheel and stiff mounts - and it doesn't bother me - I was just worried something might be wrong (i.e., out of balance flywheel). I guess I expected more vibration throughout the rpm band, not primarily all at 2-2300 rpms. Any speeds outside of that are quite smooth.

I've even heard of people complaining that lightened flywheels give rough idles, but it idles just as well as it ever did.

Thanks for the feedback guys!