91 Yamaha Big Bear 350 rear axle problems

[redneck_rolemodel]

My big bear makes some crazy grinding/clanking noises when backing up. I am guessing that this is a fairly common problem since I am having a pretty hard time finding parts and when I do they are very expensive. Does anyone have any advice? What all is there out there for interchange?

My big bear also has some other issues....if I am running it all day, I will have to change the spark plug at least once because it will foul one out.

The rear end has been making this noise for over a year now and you can actually feel it through the machine also. My quad is not used for play but only work...search and rescue, running around the property pulling parts (80 acres), plowing snow, spraying weeds, fertilizing, and fencing. Once on a search and rescue mission while coming back on the gravel roads back to the trailers at top speed there was a loud bang like it bounded up and popped loose and continued going but it was loud and felt it very well. Has anyone else had these kinds of problems?