A drive shaft loop is what it sounds like. Its a loop usually made out of steel rod or tubing that goes around the drive shaft and atatches to the cross member on the frame. What it does is prevents the drive shaft from flying out from under the truck in the case that you break a U-joint. You will see alot of drag cars and other high HP vehicals that have them. I know for a fact its manditory in Truck Pulling but not sure about in Mud Bogging. You would need a long loop if you have a flexy or long suspension travel in your lifted truck so that the drive shaft doesn't hit it at all.