what will make the 04 polaris 500 ATP 4X4 just quit pulling when you are riding it but when you put it in 4wd it will move so what could be the problem with it some people have said that ot could be the rear end and then some other people say's it could be the tran's out of it so what do you think it could be

 

Rear prop shaft coupler splines that go to the rear differential have stripped out from lack of grease,water and corrosion.Common problem on the Atp and Magnum because of the hard to see grease zerk through the holes of the box frame. Usually the diff spines are ok as it's harder steel. Item #15 in the parts break down.