Hello all, new to the forum. I have a 2005 Brute force 650 that I recently picked up for $800. Dont know anything about it other then it lost compression. I just recently rebuilt the top end. I started it up and it fired fine. I let it warm up and then went to drive it and it will not move. It goes into gear fine, but makes a grinding noise. Not like grinding the gear but like something is loose grinding and it will not move. I also noticed the MPH goes up as if it was moving... I clicked the 4x2/4x4 switch and put it in 4x4. For some reason I figured id try it in 4x4. It moved fine both forward and reverse. I put it back in 2x4 and same thing, wouldnt move. I dont know much about the driveline of this quad but it sounds almost as if there is two pulleys and whatever runs between the two is off..But it is weird that the thing moves in 4x4... Also, I checked the rear diff oil and it was bone dry. I fill with some oil and noticed it all pouring on the ground. There is a small hole in the bottom of the diff. Would not having any fluid in the rear end cause this or what could it be?