I realize this is a Polaris forum and all but I've seen other ATV makes listed in people's signatures so I was wondering if someone has any experience with this particular model. I actually signed up on a Yamaha forum when I repaired my friend's Bruin back in the spring but didn't get allot of feedback from that site.
This may be a generic "later model" ATV question. My '97 Xplorer 300 has a straight rear axle and is chain driven. Photos from Google indicate that later model Polaris ATVs also use a driveshaft coming off the transmission going to a differential like this Bruin.
After I cleaned the carburetor from sitting for three years, replaced the broken steering knuckle, rotor, caliper mounting bracket, brake pads and some broken brake hardware. Before turning it over to him I decided to have some fun with it and make sure it was going to be OK. That's what inspired me to get my own ATV which turned out to be a Polaris Xplorer 300.
Anyway while I had it, I decided to see if I could get the cable operated rear drum brake to function. This thing has two cables. One leading from the brake handle and one from the foot peg that tie to a mechanism at the drum. What a stupid setup! And to think my '97 Polaris uses a hydraulic rear disc brake and it's ten years older!
If I remember the cables looked awful and really needed to be replaced or at least taken off and lubricated. The springs also were in bad shape so I did the best I could do with it. But I managed to get the foot pedal to work (somewhat) but never had any luck with the hand brake cabel.
Back in the summer his daughter was riding it and the rear end started to knock like crazy, like driving on a flat tire. He says he removed the rear shoes and it was fine afterwards.
Now he says the differential is slinging oil and it's making an ungodly metal to metal noise.
Here is my guess. When the axle wobble initially occurred, sounds to me like one of the bearings busted. Why removing the shoes "cured" this I don't know.
Now after running it for some period of time, the worn bearing has shredded the seals. The metal to metal noise he is hearing may ball bearings that have denigrated and it gotten between the ring and pinion gears?