You can use a locking unit, or you can use the Ofna diff locking fluid. They have some thats like 150,000 wt. Its just gonna lock up the tires. So that both right and left spin the same number of rotations at any given time. Thru turns this can be a problem. However, if you have POWER, you can rip the back end loose, and slide it around. But in general, its used for climbing, serious off road, and kills your steering radius.

Matt