help!!!with drive train

i was wondering whats wrong with my atv its a yamaha kodiak 400 2002. i was riding and the whole rear end locked up. so i put in high and got home. here is whats wrong the four wheeler.it goes foward in the wrong gears such as park, neutral, and it will not reverse in any of the gears.??? i was wondering what was wrong i m thinkin its the middle drive gear but i m not sure. do you have any answers???


thanks.