Revolution Gear and Axle, Replacement series, Rear axle shaft for GM 12 Bolt Truck 73-81 1500 4WD, fits both Left and Right side, 31.43 Inch 30 Spline (OE# 14071750 / Hollander# 447-1063). Revolution replacement series axles are made from 1541H Steel and utilize a state of the art computer controlled heat treated process. The use of better material and better heat treating process gives our replacement axles a 10 Percent increase over the OEM axles.