What's the easiest way to determine the gear ratio in late 1930s axles? The 1/2-tons could have the standard 37-9 (4.11) ratio or an optional 42-11 (3.82) ratio.

My 1937 shop manual mentions serial numbers stamped on differential carrier, with the optional 3.82 axle having an "F" prefix. Does this always hold true and where is the stamp supposed to be located?


1959 Chevrolet 3800 Pickup
1937 Chevrolet GC Panel
Can you still call it a barn find if it's your barn?