My rtv has about 30 hours, rattling worse every day. Raise the bed and check the front transmission shaft yoke, mine has about 1/8 inch of play. If I put my hand on the front drive shaft at the u-joint, with it idling in neutral, it quiets right down! It won't rattle in 4wd because there is load on the shaft. I think there needs to be support for the front shaft near the u-joint!