His trucks have a CAD front axle which can be a problem. Repairing it is not that expensive so I agree with the above. I really like my CAD because it is shift on the fly. I can engage the front axle and 4 wheel drive without having to get out in the cold and wet to do it. There would be very little if any difference in mileage with manual locking hubs vs the CAD setup. Not worth the cost for most people.