need help 2000 polaris 325 magnum

i have a problem with my polaris 325 magnum when i put it in gear to ride it the rear wheels wont turn the driveshaft turns as i race the engine but the rear wheels wont lock in and turn i feel like something in the rear chunk is broken but was wondering if anyone here has any idea what i need to repair or what i need to be looking for any help would be appreciated thanks joe

Thanks for all the replies and help.i took off the rear end of the atv and tore it down and found the splines on the axle and in the axle housing where wore off keeping the back wheels from turning.so where do i get an axle and housing.[bleep] where is a cheap place to get a used rear end for the thing.any help out there?