There's nothing else to make noise on the rear wiper other than it's motor/transmission. The arm fits on the tapered motor shaft, which has small splines/teeth on it to keep the arm from slipping and to provide a means to adjust the arm. A 13mm(?) nut holds the arm in place on the shaft.
When all is said and done, the rear wiper on the Gen II's sucks unless modifications are made to the motor's mounting and/or arm. I've cut an 1/8th inch off my arm stops and use an expensive ($21) Bosch Icon blade and I get about 98% coverage on my rear glass and the blade doesn't get caught in the space between the glass and the metal part of the lift-gate. If I also remove the rubber motor mounting bushings and mount the motor solidly to the lift-gate I might get 100% coverage, but at the cost of more noise, It's not worth messing with it to get 2% more coverage. I rarely use the rear wiper anyway. The Bosch Icon blades last a long time (for multiple years) so the $21 price is worth it.