Re-gear targets for 37" tires
These restore your original gearing (from a ~31" stock tire). If you tow or want more low-end than stock, go one step numerically higher.
| Your stock axle | Ratio to restore | Closest common gear |
|---|---|---|
| 3.55 | 4.24 | 4.30 |
| 3.73 | 4.45 | 4.56 |
| 4.10 | 4.89 | 4.88 |
RPM at 65 mph on 37" tires
Cruising RPM in a direct-drive top gear, so you can see how each ratio feels on the highway.
| Axle ratio | RPM at 65 mph |
|---|---|
| 3.55 | 2,095 |
| 3.73 | 2,202 |
| 4.10 | 2,420 |
| 4.56 | 2,692 |
Which way should you lean?
- Daily driving / highway: the restore ratio above keeps your RPM and MPG close to stock.
- Towing or hauling: go one step numerically higher (for example 4.10 instead of 3.73) for stronger low-end, accepting a little higher cruise RPM.
- Mostly light and highway miles: you can stay a touch lower for a calmer cruise, but expect softer acceleration under load.
Dial in your exact numbers, including your real tire diameter and transmission gear, with the gear ratio calculator and the tire size calculator.