Jeep Regearing Explained: Gear Ratios, When to Regear, and What It Costs
Quick Answer
Bigger tires rob your Jeep of acceleration, fuel economy, and drivability. Regearing the axles restores the mechanical advantage the engine needs to spin heavier tires efficiently. Here is everything you need to know about Jeep regearing.
Why Bigger Tires Require Regearing
When you install taller tires on your Jeep, you are effectively changing the final drive ratio that the engineers designed the drivetrain around. The factory gear ratio is calculated to keep the engine in its optimal RPM range for the stock tire diameter. When you increase tire diameter, the engine RPM at any given speed drops. A 3.6L Pentastar JL Wrangler with the factory 3.45:1 gears and 32-inch tires cruises at roughly 2,100 RPM at 70 mph. Install 35-inch tires without regearing, and that same speed drops the engine to approximately 1,900 RPM, which is below the torque peak of the Pentastar.
The symptoms are immediately noticeable: sluggish acceleration from stops, the transmission constantly hunting for gears on mild inclines, difficulty maintaining highway speed, and a measurable decrease in fuel economy because the engine is lugging outside its efficient operating range. The automatic transmission exacerbates the problem by downshifting more frequently, which creates the annoying gear-hunting behavior that plagues every Jeep owner who installs big tires without addressing the gear ratio.
Understanding Gear Ratios
A gear ratio describes the relationship between the number of teeth on the ring gear and the pinion gear inside your differential. A 4.10:1 ratio means the driveshaft rotates 4.10 times for every one rotation of the axle shaft (and wheel). A numerically higher ratio like 4.88:1 means the driveshaft spins more revolutions per wheel rotation, which multiplies torque but reduces top-end speed. A numerically lower ratio like 3.21:1 does the opposite.
When you install larger tires, you need a numerically higher gear ratio to compensate for the increased tire circumference. The goal is to return the engine RPM at highway speed to approximately where it was with the stock tire and gear combination. This restores acceleration, towing capability, and fuel economy to factory-equivalent levels.
| Tire Size | Recommended Ratio (Manual) | Recommended Ratio (Auto) |
|---|---|---|
| 31-32" (Stock) | 3.73 or stock | 3.21 - 3.73 |
| 33" | 4.10 | 3.73 - 4.10 |
| 35" | 4.56 | 4.10 - 4.56 |
| 37" | 4.88 | 4.56 - 4.88 |
| 38-40" | 5.13 - 5.38 | 4.88 - 5.13 |
The Regearing Process
Regearing involves removing the differential covers, extracting the existing ring and pinion gear sets, and installing new gear sets with the desired ratio. Both the front (Dana 30 or Dana 44) and rear axles (Dana 44, Dana 60, or equivalent) must be regeared together to maintain proper driveline synchronization in four-wheel drive. Mismatched ratios between front and rear axles cause binding in 4WD and will destroy transfer case components.
The job requires specialized tools including a dial indicator for backlash measurement, a bearing puller, a pinion depth gauge, and a press for bearing installation. Setting up the ring and pinion with correct backlash (typically 0.006 to 0.010 inches), pinion depth, and bearing preload is a precision task that directly affects gear noise, wear patterns, and longevity. This is not a beginner project. Improperly set up gears will whine, overheat, and eventually fail, often catastrophically on the trail.
Professional regear shops typically charge $1,200 to $2,000 for a complete front and rear regear, including parts and labor. The gear sets themselves run $250 to $400 per axle, with master install kits (bearings, seals, shims, marking compound) adding another $100 to $200 per axle. Shops that specialize in Jeeps and off-road vehicles will have this job down to a one-day turnaround.
Choosing the Right Brand of Gears
Ring and pinion quality varies significantly between manufacturers. Yukon Gear & Axle is the industry standard for aftermarket Jeep gears, offering excellent metallurgy and tight tolerances at a reasonable price. Their master install kits include all necessary bearings, seals, and shims for a complete installation. Revolution Gear & Axle is a newer competitor with a strong reputation and competitive pricing. Motive Gear provides a budget-friendly option that works well for moderate use but may not hold up as well under extreme loads.
For Jeeps that will see serious off-road abuse, competition rock crawling, or heavy towing, genuine Dana Spicer gears from the OEM manufacturer are worth the premium. Their heat treatment and quality control standards exceed aftermarket alternatives. Regardless of brand, always purchase a quality master install kit rather than reusing old bearings. The cost difference is minimal and the risk of premature failure from worn bearings is not worth saving $50.