Changing Gearbox fluid On 800 X2?

[Sunset Ed]

I have a Polaris 800 X2, an 07 model. I submerged it. I changed the oil many times, then changed what I thought was the tranny fluid. I also changed the front drive oil. When I slow down now, I hear gears grinding. I wondered if it was the ADC(auto descent control), but now wonder about the rear gear case. I looked around and even had online access to a manual, but do not see where to change that at. The only drain plug and fill plug I saw were the ones I thought went to the tranny. I know it must have been the tranny as the amount of oil it used when I changed the oil in it.. The gear box uses less I believe.
Ed