Answer: There are several things that can go wrong with a four-wheel drive locking hub. The most severe and common problem is that the hub won’t engage the front differential. This can be caused by worn parts or by mud or water entering the hub. This will basically make your four-wheel drive vehicle useless since your front wheels can’t be engaged. Another issue with locking hubs is that the hub can get stuck in lock and won’t disengage the front differential. This will lead to excessive wear of parts, excessive wear of tires, and poor fuel mileage.