[Yukon Jack]

Was the highway snow packed?

In our era of trucks, 4Hi shouldn't be used on a highway unless it is snowy or I guess maybe wet. If you use it on a dry surface you can get bind in your drivetrain as these transfer cases don't allow any differentiation to happen. If your drivetrain gets some bind in it you can definitely feel it - not sure if that is what you are dealing with or not.