What Is the Difference Between 3.55 & 3.73 in Ford Trucks?by Vern Hee
The numbers 3.55 and 3.73 refer to Ford truck axle ratios. The axle ratio tells you the number of revolutions the drive shaft makes compared to the rear axle. For a 3.55 axle ratio, the drive shaft will turn 3.55 times for every one revolution of the tire.
Ford Axle Ratios
Ford offers two axle ratios for their F-150 trucks; the 3.55 is standard and the 3.73 is optional. Ford offers different axle ratios to improve on hauling capability. The numerically higher number is the lower ratio.
A numerically high axle ratio means your drive shaft makes more revolutions and therefore the engine works harder and uses more gas. According to Truck Digest, going from a 3.55 axle ratio to a 3.73 will cost you a quarter mile per gallon in the long run. This manifests itself on long hauls.
Trucks that respond best to heavy loads typically have an axle ratio of 3.73, 3.92 or 4.10. The numerically high axle ratio like the Ford 3.73 provides the truck more low speed wheel torque and makes it easier to get the vehicle moving.
- the largest wheel of a truck image by Ivan Hafizov from Fotolia.com