a value determined based on observation or experimentation the summing node 69 determines the difference of the two inputs 64 and 72 and outputs a value 74 indicating the amount of front axle slip error the rear axle slip value 68 is sent to summing node 70 summing node 70 receives a second input 71 that represents a predetermined or target value for allowable slip at the rear axle which like the input 72 is an empirical value the summing node 70 determines the difference between the two inputs 68 and 71 and outputs a value 75 indicating the amount of rear axle slip error the rear axle slip error 75 is sent to a rear axle controller 76 the rear axle controller 76 generates a command signal 77 that includes a target torque value for the rear axle in fig3 the label msoh_ctcs is used to identify the signal 77 the front axle slip error 74 is provided to a front axle controller 78 the front axle controller 78 uses the front axle slip error 74 to determine an amount of torque to apply to the wheels connected to the front axle note that a large in relative terms value for the front axle slip error 74 is indicative.