Just a heads up on if anyone is getting a continuous 'Low Toner' message or continuous 'Add Toner' message on a 3550. Found that the side gears on the toner drive on the whole unit that pulls out can be easily popped out if someone jams the toner in. They don't break, but can pop out of housing.Easy fix though. 2 tabs on top and 2 on bottom. Then just reseat the 2 gears.