If it is an older axle it is an Eaton brand, GM corporate axles were vacuum. It wouldn't surprise me that a GMC/fire truck would have the Eaton. My 1957 Chevrolet shop manual has tear-down for both. I checked the 1954 Chevrolet Truck specs on the GM heritage site, they list only one 2 speed axle, it being a vacuum shift, that doesn't mean that GMC didn't use the Eaton.
Last edited by 78buckshot; 01/21/2025 6:21 PM.
