From what I understand the manual says about drivertain damage if you drive on dry pavement with locked central differential on Limited or locked rear differential on Trail. And it's just not recommended for SR5 and Trail to use 4Hi on dry pavement. Correct me if I'm wrong but I got a feeling that transfer case is more forgiving that cental or rear differential and turning on dry pavement with 4hi on Trail or SR5 would just cause unnecessary wear for driveline and front tires, but it won't immediately damage drivetrain. Sort of like towing a heavy trailer or driving overloadrd truck. So it's not a good idea for Trail and SR5 to use 4hi on dry pavement (and there is no reason why to use 4x4), but it perfectly fine to use 4hi on wet pavement or on pavement with patches of snow in winter. As I said that what I got from everything I've read on the topic so far, please correct me if I'm wrong.