I have a Pettyr nasty vibration that has me nuts trying to isolate it. it is mostly noticible at the tail boom & vertical fin but the whole machine shakes. The tail boom is actually vibrating up & down but when your looking at the vertical fin it has a noticeable side to side vibration.

This is what I have already tried Checked the tail rotor shaft for end play. Found none. Checked balance of blades. good, changed main shaft and hub,swapped out the belt, tighten every nut & bolt on the head & finally checked the phasing.

does anyone have any suggestions!!!

thanks in advance
Santonomos