See Figure 1
From 1970 to 1973, the axle serial number for 1 / 2 ton Chevrolet and GMC trucks can be found on the bottom flange of the carrier housing. For 3 / 4 and 1 ton, the number is stamped on the forward upper surface of the carrier. For all 1974-79 trucks, the rear axle numbers are on the front of the right rear axle tube inboard of the upper control arm bracket, except for Dana-built axles, which are stamped on the rear surface of the right axle tube. Front axles on 4 x 4s are marked on the front of the left axle tube.