Well, my Polaris 360 is only 1 year old and the bearings are shot. Found the Polaris not moving and thought it was sediment caught in the gears again (happened once). After disassembly I found no pebbles in the gears. Further inspection found the ball bearings missing on the single wheel side. Some of the other bearings had play in them which I plan on replacing as well. Amazon had the bearings, I bought a pack of 4. Everything else looked ok inside so I am just going to replace the bearings and see what happens.