I recently bought a used Mule. I road it with the previous owner and it ran fine. I got home and it ran with no issues until I switched the lever from 4 to 2 wheel drive. It made a loud bang and temporary stopped moving when I took off. Then the issue continued sporadically. I switched back to 4 wheel drive after the second occurrence. However, it is still has the issue. Maybe every 30 feet of travel it happens.