One of the most common questions we get is: “What gear ratio should I run?” The answer depends on your tire size, driving style, and what you want your vehicle to do.
Why Gear Ratio Matters
When you install larger tires, your vehicle’s effective gear ratio changes. Larger tires act like taller gears, which means:
- Slower acceleration
- Higher RPM needed to maintain speed
- Reduced towing capacity
- Decreased fuel economy
- More strain on your drivetrain
Re-gearing restores your vehicle’s performance by matching the gear ratio to your tire size.
Understanding Gear Ratios
Gear ratios are expressed as a number like 3.73, 4.10, or 4.88. The higher the number, the “lower” (or shorter) the gear:
- Lower numerical ratio (3.21, 3.55) = Better highway fuel economy, less acceleration
- Higher numerical ratio (4.56, 4.88, 5.13) = Better acceleration and towing, more RPM at highway speed
Recommended Ratios by Tire Size
Here’s a general guide for Jeep Wranglers and similar vehicles:
| Tire Size | Stock Ratio | Recommended Ratio |
|---|---|---|
| 31” | 3.07-3.55 | Stock is usually fine |
| 33” | 3.73-4.10 | 4.10-4.56 |
| 35” | 4.10-4.56 | 4.56-4.88 |
| 37” | 4.56-4.88 | 4.88-5.13 |
| 40”+ | 5.13+ | 5.13-5.38 |
Factors to Consider
1. How You Drive
- Mostly highway: Go with the lower end of the recommended range
- Mixed driving: Middle of the range
- Mostly off-road or towing: Higher end of the range
2. Transmission Type
- Manual transmission: Can run slightly taller gears since you control the RPM
- Automatic transmission: Often benefits from slightly lower gears
3. Engine Type
- 4-cylinder: Benefits from lower gears to compensate for less torque
- 6-cylinder or V8: More flexibility in gear choice
4. Do You Tow?
If you regularly tow, go with lower (numerically higher) gears. The improved torque multiplication makes a huge difference when pulling a trailer.
The Re-Gearing Process
Re-gearing involves:
- Removing the differential covers
- Removing the old ring and pinion gears
- Installing new gears with proper setup
- Setting correct backlash and gear pattern
- Installing new bearings and seals
- Breaking in the new gears properly
Important: Both front and rear differentials should be re-geared at the same time to maintain proper operation of your 4WD system.
Cost vs. Benefit
Re-gearing isn’t cheap, but the benefits are significant:
- Restored (or improved) acceleration
- Better fuel economy than running wrong gears
- Reduced drivetrain strain
- Improved towing capability
- More enjoyable driving experience
If you’ve installed larger tires and your vehicle feels sluggish, struggles to maintain highway speed, or seems to work harder than it should, re-gearing is the solution.
Get a Quote
Not sure what gear ratio is right for you? Give us a call. We’ll discuss your setup, driving style, and goals to recommend the perfect ratio for your vehicle.