2012 rzr 800 rear diff pinion nut

Was plowing slowly and rear end locked up, front 4 x 4 works. Freewheeling backwards in all gears including park?? Have seen a lot of posts abou pinion gear nut loosening? I am assuming the pinion gear is in a place to wedge it from rotating one way? Axle shafts removed and same result…………….i dont see a good youtube video on removal of rear diff!? Thanks