There's a really big difference in the 1/2 ton rear, compared to the heavier ones. 3/4 and 1-ton rear axles are similar, with the center section being interchangeable. 3/4 tons use single rear wheels and slightly smaller brakes than the 1-ton, while the tonners run dual wheels and larger diameter, wider brake drums. They both run "full-floating" hubs with two large bearings and eight lug bolts, where the axle shafts bolt in from the outside of the hub. The 1/2 ton runs a "semi-floating" hub with a single wheel bearing inboard of a flanged axle shaft with six lug bolts. The axle is retained by a C-shaped washer that fits a groove on the inboard end of the axle. Virtually nothing interchanges between the 1/2 ton and larger rear ends.

The 1/2 ton axle runs a standard gear ratio of 3.90:1 and there is an aftermarket gearset to change the ratio to 3.55:1. The bigger rear end can have 4.11, 4.57, or 5.17 ratios, The 4.11 is as scarce as a chicken with lips! Good luck finding one! The 3/4 ton will probably have the 4.57, which is good for pulling medium-sized stumps, especially combined with the crash-box granny gear on the 4-speed SM-420 transmission. There are some later-model full-floater rear axles with 8-lug hubs, but most of them are too wide to fit inside the old Chevy pickup fenders properly.
Jerry

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