Although the earlier model Roomba brush deck did not suffer the same fate as the Cleaning Head Module in the 500/600 Roombas they still suffer from some debris entry into the brush gear assembly as well as the diameter of the gear shafts wearing down while the opening wears larger.  I offer brand new brush decks both single and dual dirt detector hole models with the 3 ball bearings installed for your 4XX and 4XXX model Roombas and the Dirt Dog brush deck that has no Dirt Detector .  Just specify one or two Dirt Detector hole brush decks when ordering a 4XX, 4XXX Roomba or that you are ordering the no dirt detector Dirt Dog brush deck.  The decks are $78 including USPS shipping.  Send a paypal to:  e_vickery@bellsouth.net

Also available for the 4XX, 4XXX, and Dirt Dog brush deck, is a complete gear set with the 3 ball bearings installed.  You can order this option for $55 including USPS shipping.  Just paypal to the above email.

I also offer just the 3 sealed ball bearing set so that you can install the bearings in your own 4th Gen or earlier Roomba.  Just paypal me $28 to the above email.