Mike - From what I could find, the stock 5-speed in that C70 fire truck would be a direct drive 1 to 1 output unit, not an overdrive unfortunately. Appears they are identified as an Eaton/Fuller FS-5205.

That info should help you find more detailed info on the transmission.

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)