Also while you are at it, check inside the diff and look at those gears. My Savage used to blow those out a lot, but that was when they were still using the 2 gear bevel type. Ever since I upgraded to 4 gear bevel types I haven't had a problem for years. Maybe your truck just got a bad set of gears with it if it is still newish. These things happen, not a lot of money to replace those.