My brother and I both have 4x4 titans. We were talking about the 4x4 system today after lunch. He said they need to be put in 4x4 about every month or so--which I agree with also. However, he said that it would not hurt the truck to drive in 4-hi on dry pavement if you don't get above 50mph. I disagreed with him on this. My dad agreed with him also. Both of them said it would hurt the trucks to drive them in 4-lo on dry pavement, but not in 4-hi. Whom is right in this discussion?