About a month ago, the new one developed similar noises, so I went to the source of all knowledge, google and found this forum, and Jeffs' excellent teardown/lubrication post. Everything he said is true - I just got done tearing mine down, lubing and rebuilding, and it's now quiet. I think the critical part is the metal rails at the bottom of the conveyor - as the motor drives the moving conveyor down, it pushes under the litter and if litter had caked on these rails, that's a major source of noise. I used sandpaper to get them really clean, and then the silicone spray recommended to lubricate them. Our cat is now about 13 lbs, and used it from day 1 (i.e. the day we brought her back from the shelter) with no problems at all.
One question - any idea how to open the motor connector? I couldn't easily figure out how to release the conveyor motor from its wires. This made my cleaning a little more difficult, but not impossible.
Two important things to take away here - Petsafe support is pretty good and very willing to replace the SC, but they really don't know what causes noise, nor a good cleaning/lubricating guide. And, of course, keep it cleaned and lubed per Jeffs' outline.
Oh, and I write US English (born in NYC, live in CA), but the board only offers British. Although I can read British, even if they spell funny
