Quote:
Originally Posted by scdrj
The rotors do not inherently rattle. The rattle is a product of the lash between the rotor coupling gears as the experience continuous drive to coast. The spring coupler loads, and unloads in an attempt to silence what would otherwise rattle. The slack in the spring coupler actually caused as many problems as it attempted to fix by facilitating the very same rattle in many units. The groves in the shaft "themselves" are of little consequence, but the shrapnel they make has shown the ability to enter the drive rotor bearing in the front directly behind the coupler.
The solid coupler allowed rattling in several units too, but at least it did not make metal filings. I assume GM or Eaton threw a party when one of their brilliant engineers figured out that a heavy greased spring unit would make better all things. The grease would lubricate making the tension more linear with less wear to the shaft. It would help damp the spring coupler. And, it would catch the shrapnel. YEAH! 
Only one small problem... It is not 100%. Hence my car. It turned out to be a greased spring unit. The grease caught all the powder, but had slung outward to create a grease halo of sorts. The accumulation settled at the bottom of the bore until substantial enough to start drifting back. I'm sure operating temps helped this process. The grease actually helped all the metal make its way directly to the rotor bearing. BTW, my pilot shaft looked as bad as any of them at 11k miles. Three dealerships and GM customer service acknowledged my problem, but refused to do anything about it. While you technically void your warranty by having someone helpful repair your car, do not worry....that warranty at worth a squirt of pi$$. |
I didn't remember the actual cause of the inherent 'rattle', so I simply referred to it as the 'rotor rattle'. Thank you for pointing it out that it's actually the rotor gears and their gear lash that is the source of the 'rattle' that the isolator is trying to minimize before it gets transmitted to the drive belt.