Originally posted by conker69:
It is best to shift while on level ground or at least somewhat level in order for the hubs to lock. Once the hubs are locked they stay locked until you move in the opposite direction in 2H. But as long as they are locked, you can shift into 4H at any speed.
Hate to be anal, but the hubs don't lock, they engage. Hubs can only be locked if the vehicle has manual hubs and you actually put them into the locked position. It really doesn't make a difference if you are on level ground or not. The hubs don't engage until the axle starts to rotate, in either direction.
-Michael