The mixer has been really noisy for as long as
I can remember. Peaking from behind the ring gear of the final drive is
the reason why. The eccentric shaft adjustment is done with that
nut/setscrew/shaft assembly. The adjustment of this shaft controls the
gear mesh and ultimately the noise of the transmission. Someone in the
past did not have the correct tool to hold the shaft while tightening the nut
and ruined the head. The shaft slipped and the transmission ran noisy.
I replaced the shaft, $90 shipped.