The Stovebolt Site Forums The Shop Area Driveline Rear end ratio for 55 Cars and Trucks w overdrive

Depends on the year of the truck. '55 trucks did have a 3.90, but a 4.10 became an option in '56.
Also, just a quick gear ratio term explanation; 3.90 would be a higher gear than 4.11. A low number would be a high gear, larger numbers are a lower ratio.