I picked up a 450es from my grandpa that wasn’t being used and wasn’t running the greatest. It has been sitting now for like 6 months and when I went to pick it up we couldn’t move it. I can manually shift if it through the gears as well as electronic shift it, but it won’t move. Even I’m nuetral, the tires are locked up on it…should I be looking more at the rear differential or the rear brake drum?