The 4x4 S10 is wider, and the ZR2 S10 from '98-'04 is even wider than the standard 4x4, and is a heavier duty axle. It's a narrowed version of the '88-'98 full size truck axle. Also, on 2wd S10s, there was a lighter duty axle found under 4 cylinder trucks.
Also of note, the Trailblazer axle has a different bolt pattern, 6 x 5, not used on any other Chevrolet truck. The same rear is also found under the Envoy, late Bravada, and the Rainier.
