transmission??? g1 outty

Got a 07 outty max. Was riding about 35-40 mph yesterday on the road and my back tires just locked up. And i slide to a stop. the bike never died. But when it finally came to a stop, I hit the gas and it wouldn’t go anywhere. I put it in reverse and it did just fine, back to high and it did just fine but it was making a noise like something was loose internal when it was rolling. So I parked it and we went and got the truck. When we got back to the bike I cranked it and it pulled on the trailer and when I got to the house off the trailer just fine. Help please! Keeping my finger crossed it’s an easy fix!