Roomba Model 4210. There is grinding sound when the Roomba operates and while the vacuum suction is working, the "front" wheel barely turns. The end of the bristle brush (the square end) fits into a square hole and that hole appears to have been stripped and distorted. How do I get to these gears to replace them?

Dan Jenkins, March 2007

Basically find another unit on Ebay, take it apart, and take notes for re-assembly. There's quite a chop-shop Roomba industry on Ebay. IRobot designed a clutch assembly for the brush drive that basically never slips, so the spur gears get trashed. The software design is good, the bells-and-whistle factor is high, but the implementation, QA, and durability is poor. Sorry. We have several and I'm tired of fixing them.

Lee, April 2007