How do you adjustment on the fifth wheel on a mack truck?

It really depends on the model of the fifthwheel. All of the maintenance procedures are online and free. you must know the manufacturer and model of the fifth wheel. Examples of common manufacturers are, Fontaine, Holland/Simplex/ASF, Jost. You will need a 2" kingpin to properly adjust it. Be very careful because these fifthwheels are spring loaded and can hurt you. The adjustments are straight forward and pretty simple no matter which model is installed on the truck.