An agricultural tractor rear suspension system having a longitudinally extending suspension arm pivotally coupled to the tractor chassis at one end and to a planetary gearbox at the opposing end, a differential connected to the tractor chassis, and a driveshaft rotatably supported at one end by the planetary gearbox and supported at the other end by the differential housing wherein the driveshaft is configured to resist suspension arm flexural by communicating tensile and compressive forches from the suspension arm to the tractor chassis.