Rear wheel assist for a self-propelled scraper

A work vehicle for performing a work operation, the work vehicle comprising:

• an articulated frame having a front frame section and a rear frame section that are pivotally coupled to one another, the front frame section having left and right front wheels and the rear frame section having left and right rear wheels;
• an engine mounted to the front frame section;
• a main transmission mounted to the front frame section being driven by the engine, the main transmission having an axle for driving the left and right front wheels;
• a reversible variable displacement pump mounted to the front frame being driven by the engine;
• a left hydraulic motor being coupled to the left rear wheel for driving the left rear wheel;
• a right hydraulic motor being coupled to the right rear wheel for driving the right rear wheel;
• a two-position engagement/disengagement valve being hydraulically positioned between the left and right hydraulic motors and the reversible variable displacement pump, the engagement/disengagement valve has an engagement position for directing hydraulic fluid to and from the left and right hydraulic motors to and from the reversible variable displacement pump, and a disengagement position for hydraulically disengaging the left and right hydraulic motors from the reversible variable displacement pump;
• first and second supply/return lines extending between the reversible variable displacement pump and the engagement/disengagement valve for directing hydraulic fluid to and from the engagement/disengagement valve;
• third and fourth supply/return lines extending between the engagement/disengagement valve and the left and right hydraulic motors for directing hydraulic fluid to and from the left and right hydraulic motors;
• and
• a controller for shifting the engagement/disengagement valve to its engagement position when a floor pedal on the front frame is depressed by an operator, the controller shifts the engagement/disengagement valve into its disengagement position when the floor pedal is released.