Abstract: A torsional shock absorber dampens rotary shock loading on a well drill string. An outer housing has drive splines on an inner surface. A mandrel is located within the outer housing and has drive splines on an outer surface that fit between the drive splines on the inner surface of the housing. Dampening bars are positioned longitudinally between the splines of the outer housing and the splines of the mandrel to absorb shock from non-uniform torsional loading at the drive interface between the outer housing and the mandrel. A balancing piston is located within the tool to compensate for pressure difference between drilling fluid pressure and lubricant contained within the shock absorber. A thrust bearing assembly is provided to accept axial thrust loads from the outer housing and transfers the load to the splined mandrel. A retainer transfers tensile loads from the housing to the mandrel through the thrust bearing.