08 Rzr Rear diff/axle upgrade

I recently snapped a rear axle on my 08 RZR. I talked to a buddy who had a 11 rear axle for me, went to put it in and it did not fit. I am wondering if it is possible to upgrade the gears in my rear diff so they accept the newer axles. only reason I would like to do this is so that I have more years of available parts for my machine. Thank you