How to Figure Out the Gear Ratio on an F-150by Robert Bayly
The Ford F-150 was introduced in 1975. One of the best-selling vehicles of all time, there are more F-150 trucks on the road than any other brand. Over the years, the F-150 came with an assortment of rear ends and gear ratios depending on engine size and options. Knowing the gear ratio of your F-150 is important if you have to replace the ring and pinion gears due to breakage, or if you want to change gear ratios.
Locate the "Vehicle Certification Plate" on the inside of the driver's door near the door latch. The axle code is printed under "Axle" or "Ax." You can use the chart provided in the first resource below to cross reference the axle code. You can verify the gear ratio using the next two steps.
Locate the axle tag on the rear axle. It is a small metal tag attached to one of the differential cover bolts. The differential cover is the metal cover on the back center of the rear axle. It is held on with a circular pattern of bolts. Older F-150s do not have a cover; they have a differential carrier. Either way, there is still a circular pattern of bolts.
Write down the number in the lower left-hand corner of the tag. It will look like "3.23" or "3.50." This is the gear ratio. If there is an "L" in the number, for instance "3L23," it is a limited slip differential.
- Limited-slip differentials provide power to both tires. If one tire starts to spin, power is transferred to the other one. Non-limited-slip, or "open" differentials, provide power to one tire only. If it starts to spin, the other tire will remain stationary. Lower (numerically higher) gears are better for pulling and acceleration. Higher (numerically lower) gears are better for highway driving.
Things You'll Need
- Jack (optional)
- Jack stands (optional)
Robert Bayly, based in Apple Valley, California, began writing in 2010, his "how to" articles can be found on eHow. With more than 15 years in the auto industry, Bayly has been an auto and diesel mechanic, service writer and parts manager. He received certificates from Pontiac (parts system), Cat Diesel (engine service), Saab and Fiat (parts- warranty system).