GM 12 Bolt Axle Specs & Information

GM 12 Bolt Axle, Differential Specs

The General Motors 12 bolt axle was used in GMC and Chevrolet pickups from 1964 to 1982. It is a semi floating rear axle with a 8.875" ring gear. Its most notable weakness is the fact that it uses C clips to hold the axle shafts in place, but this can be remedied by an aftermarket C clip eliminator kit. The 12 bolt is a 1/2 ton to 3/4 ton axle and is comfortably rated for up to 35" tall tires on the highway. A passenger car version of the axle was offer produced, but not covered in the scope of the following information.

GM 12 Bolt Specs

Applications:	1964 - 1982 Chevrolet & GMC 1/2 ton to 3/4 ton trucks
Full/Semi Float:	Semi floating rear axle
Ring Gear:	8.875"
Axle Spline Count:	30 spline
Axle Tube Diameter:	3.00"
Pinion Diameter:	1.625"
Pinion Spline:	30 spline
U Joints:	1310 series
Ratios:	2.50 - 4.56 : 1
Carrier Break:	2.50 - 2.76 \| 3.42 -4.56
Identification:	12 bolt rear cover, passenger car version has a different cover and is easily distinguishable