Tailshaft Vibration

[Driver]

We have virtually finished the build of our W115 as an endurance rally car but have a bad tail shaft vibration. All the connections, mounts, bearings have been renewed, the diff rebuilt, new drive shafts and the shaft has been balanced three times but the vibration is getting worse not better. We have eliminated every other possible source of the vibration that we can think of. Is there a secret trick to balancing these shafts?
Any suggestions gratefully received?

[newMercowner69]

Did they (balancing shop/tailshaft shop),
Add/inc the balance weights on the tailshaft?,
Did they supply&fit new universal joints?.SOME brands of universal joints are of inferior&poor quality,
Also did you check rear wheel bearings & seals?,
The seals won't cause vibration problems,
But worn &inferior quality & fitted bearings will cause vibration,
Or loose wheel nuts,
Or loose/worn hubs.

[Chai]

I had terrible vibrations when the centre bearing on the 2-piece drive shaft was worn, along with disintegrated rubber mounts on the centre bearing and the differential end.
Replaced them and all was smooth again.

[Lance]

Also look at the gearbox mount as this can have an effect on tailshaft angle, engine mounts as well, maybe diff mount, someone on here once mentioned the bushes in the ends of the driveshaft, they would have an effect on correct alignment.