Abstract: A hydrodynamic retarder control apparatus includes two valve spools, one, a retarder control valve, functions as a relay valve to control the on/off operation of a hydrodynamic retarder and the other, a regulator valve, functions to control the regulation of pressure at the hydrodynamic retarder. During abnormal periods of operation of the regulator valve, the retarder control valve will also function as a pressure control valve thereby limiting the maximum pressure at the hydrodynamic retarder.

Abstract: A hydrodynamic retarder has an outer housing and an inner housing. A planetary carrier shaft member is rotatably supported on taper roller bearings located in the outer housing. The taper roller bearings are positioned between a shoulder on the shaft and a retaining nut or fastener which is threadably secured to the shaft. A Belleville or Belleville spring is positioned between the retaining nut and the inner race of one of the roller bearings. The retaining nut is secured such that the Belleville spring is flattened thereby applying maximum force to the inner race. The force is transmitted through the first roller bearing, the outer housing, the outer race of a second roller bearing, the second rollers and the second inner race. The Belleville spring will accommodate axial movement between the retaining nut and the bearing.