The axle carrier is egg shaped. It also as a hex shape molded on one side. Loosen the two bolts at the back of the axle carrier, you can then spin axle carrier and the egg shape causes the axle and rear sprocket to move back and forth, changing chain slack.
Make sure it's set right. To tight and it could crush your countershaft seal when you hit a bump.
If it was loose enough to fall of, it may need to be replaced, or maybe too many links are in it.
A forum community dedicated to Polaris ATV owners and enthusiasts. Come join the discussion about Rangers, Sportsmans, Scramblers, Magnums, and others. Research modifications, troubleshooting, maintenance, and more!