[Trucker1967]

I was wondering if this could be a balance issue with the ring gear in the rear end not in perfect balance ...

I mean just a little bit of it being out of balance would cause a certain occilation and harmonic issues running through the springs bed and etc ... being that some have it and some dont ... sort of like how a gyro works at first it would be fine and spin even out of balance slightly but at its harmonic apex (where its most sensative) it would start to shake, buzz and its balance would get worse and worse until basic harmonic failure and fall down like a kids toy like a "Top"

I have noticed some say if they go very fast it seems to quiet down and some that go slower it also seems to stop, thus perhaps pushing it out of its harmonic balance apex (this really does seem to be some sort of harmonics problem)

Again this is just something I was sitting here thinking about and am no expert in any way.