Revolution Gear and Axle, Replacement series, Rear axle shaft for GM 12 Bolt Truck 65-69 2WD and 4WD Pick-Up, fits both Left and Right side, 30.75 Inch 30 Spline (OE# 3893605 / Hollander# 447-780). 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.