[A.T. RockDriller]

Originally Posted by factorystock

The switch is a front brake limiting valve. It reduces air pressure applied to front brakes when on the "slippery postion". I bet this truck was a short wheel base 2 axle tractor in its earlier life. It was very common for large trucks to be modified when sold to fit the need of the new owner. A power divider differential lock will say "lock" "unlock".

Yer all over it, factorystock....