## 3.54 / 3.55 and 4.09 / 4.10 / 4.11 Gears

One of the most common questions about gear ratios is: what is the difference between 3.54 and 3.55 or 4.09, 4.10, and 4.11 gears?

As our Gear Ratio Calculator explains, the gear ratio is calculated by dividing the number of teeth on the ring gear by the number of teeth on the pinion gear. Since this doesn't always end up in a nice even number, we have to do some rounding to get the final gear ratio down to three digits.

Additionally, different axles use different size ring and pinion gears that require a different number of teeth on each gear to make them turn properly. This variation in tooth number combined with a need to round up or down is what causes a discrepancy in gear ratios.

## Example: 4.09 / 4.10 / 4.11 Gear Ratios

The following table contains a list of common axles along with their ring and pinion tooth count and ratios. You will notice that while many of them are identical, a few have a different number of teeth on each gear that results in a minor shift up or down in the final gear ratio.

 Axle Ring Gear Teeth Pinion Teeth Calculated Final Ratio Dana 30 JK 41 10 4.1 4.10 AMC Model 35 / M35 37 9 4.111111 4.11 Toyota 8" 37 9 4.111111 4.11 Dana 44 45 11 4.090909 4.09 Dana 60 41 10 4.1 4.10 GM 10.5" 14 Bolt 45 11 4.090909 4.09 Dana 70 41 10 4.1 4.10 Dana 80 41 10 4.1 4.10

It is perfectly ok to run 4.09 gears in one axle and 4.11 gears in the other. The general rule of thumb for any 4x4 vehicle is for the front and rear ratios to be within 2% of each other (this amount is easily absorbed within the backlashes in the drivetrain) and the difference between 4.09 and 4.11 gears is less than one-half of one percent.

## Compatible Gear Ratio Variations

 3.54 3.55 3.90 3.92 4.09 4.10 4.11 4.86 4.88 5.13 5.14