Guide
Regearing for bigger tires
Bigger tires make your truck taller-geared: less pull, lower revs, an automatic that hunts between gears on hills. Regearing swaps the ring and pinion in both axles to win that back. Here's how much you lose, which ratio gets it back for 33s, 35s and 37s, and what the job involves.
What bigger tires do to your gearing
A taller tire covers more ground each turn. In the same gear, at the same road speed, the engine turns slower, and the push at the ground drops by the same percentage. Your axle ratio hasn't changed, but the truck behaves as if it had a taller (numerically lower) one.
| Tire jump (inches) | Taller by | Pull and revs change |
|---|---|---|
| 31 to 33 | +6.5% | -6.1% |
| 31.5 to 33 | +4.8% | -4.5% |
| 33 to 35 | +6.1% | -5.7% |
| 31.5 to 35 | +11.1% | -10.0% |
| 35 to 37 | +5.7% | -5.4% |
| 33 to 37 | +12.1% | -10.8% |
| 31.5 to 37 | +17.5% | -14.9% |
Based on nominal tire heights. "Pull and revs change" is in every gear, compared with the smaller tire.
Which ratio gets it back
To drive like stock on bigger tires: new ratio = stock ratio x new tire height / stock tire height. Gear sets only come in certain ratios, so pick the nearest one your axle is offered in.
| Stock ratio (on 31.5" tires) | On 33s | On 35s | On 37s |
|---|---|---|---|
| 3.21 | 3.31 exact 3.36 | 3.55 exact 3.57 | 3.73 exact 3.77 |
| 3.42 | 3.55 exact 3.58 | 3.73 exact 3.80 | 4.10 exact 4.02 |
| 3.45 | 3.55 exact 3.61 | 3.91 exact 3.83 | 4.10 exact 4.05 |
| 3.55 | 3.73 exact 3.72 | 3.91 exact 3.94 | 4.10 exact 4.17 |
| 3.73 | 3.91 exact 3.91 | 4.10 exact 4.14 | 4.30 exact 4.38 |
| 3.91 | 4.10 exact 4.10 | 4.30 exact 4.34 | 4.56 exact 4.59 |
| 4.10 | 4.30 exact 4.30 | 4.56 exact 4.56 | 4.88 exact 4.82 |
Not every ratio is made for every axle; check what yours is offered in. Tire heights are nominal: check the maker's published diameter for your exact tire.
"Like stock" is the safe target if you were happy with the truck before. One step shorter than the table gives extra pull for towing, heavy loads, a small engine or a manual gearbox, and costs revs and noise on the highway. If most of your driving is highway, stay closer to the table. Your own sizes and ratio: use the calculator's regearing section.
3.73 vs 4.10 vs 4.56 vs 4.88
The number is how many times the driveshaft turns for one turn of the wheels. A 4.10 set, for example, might have 41 teeth on the ring gear and 10 on the pinion. A bigger number means more pull and more engine revs. Each common step changes things by roughly 5 to 11%:
| Step | More pull and revs |
|---|---|
| 3.73 to 4.10 | +9.9% |
| 4.10 to 4.56 | +11.2% |
| 4.56 to 4.88 | +7.0% |
| 4.88 to 5.13 | +5.1% |
| 5.13 to 5.38 | +4.9% |
3.73 gears
3.73 means 3.73 driveshaft turns per wheel turn. It's the nearest common set for getting back to stock gearing from 3.55 stock on 33s, 3.42 stock on 35s and 3.21 stock on 37s (starting from 31.5-inch stock tires). On 35s it turns about 1,860 rpm at 65 mph in the example truck below.
4.10 gears
4.10 means 4.10 driveshaft turns per wheel turn. It's the nearest common set for getting back to stock gearing from 3.91 stock on 33s, 3.73 stock on 35s, 3.42 stock on 37s and 3.55 stock on 37s (starting from 31.5-inch stock tires). On 35s it turns about 2,050 rpm at 65 mph in the example truck below.
4.56 gears
4.56 means 4.56 driveshaft turns per wheel turn. It's the nearest common set for getting back to stock gearing from 4.10 stock on 35s and 3.91 stock on 37s (starting from 31.5-inch stock tires). On 35s it turns about 2,280 rpm at 65 mph in the example truck below.
4.88 gears
4.88 means 4.88 driveshaft turns per wheel turn. It's the nearest common set for getting back to stock gearing from 4.10 stock on 37s (starting from 31.5-inch stock tires). On 35s it turns about 2,440 rpm at 65 mph in the example truck below.
5.13 gears
5.13 means 5.13 driveshaft turns per wheel turn. On 35s it turns about 2,560 rpm at 65 mph in the example truck below.
What it does to highway revs
Engine rpm at 65 mph = 65 x axle ratio x top gear ratio x 336 / tire height. This example uses a 0.80 overdrive top gear; your gearbox will differ, so treat it as a comparison, not a prediction.
| Ratio | 31.5" | 33" | 35" | 37" |
|---|---|---|---|---|
| 3.73 | 2,070 | 1,970 | 1,860 | 1,760 |
| 4.10 | 2,270 | 2,170 | 2,050 | 1,940 |
| 4.56 | 2,530 | 2,410 | 2,280 | 2,150 |
| 4.88 | 2,710 | 2,580 | 2,440 | 2,300 |
| 5.13 | 2,850 | 2,720 | 2,560 | 2,420 |
Assumes no torque-converter slip. 336 converts miles per hour and inches into revolutions per minute.
Ring and pinion swap: what the job involves
- Both axles, same ratio. On a 4WD the front and rear must match.
- Ring and pinion set up by someone who has done it before. Pinion depth, backlash and bearing preload have to be set and checked; a poor setup whines and can fail.
- An install kit with new bearings and seals is normal, and the gear maker's break-in procedure should be followed.
- Check the carrier break. On many axles a carrier or locker only fits gears on one side of a "carrier break" (Dana 30, for example: 3.54 and down, 3.73 and up). Crossing it, even by one step, means a different carrier, a thick-cut ring gear or a spacer.
- Reprogram afterwards. Many modern vehicles need the new tire size and axle ratio set, for the speedometer, gearbox and stability control.
Cost varies a lot by axle, region and shop, and whether lockers or carriers change too, so get quotes for your truck rather than trusting a single number.
Questions
What does regearing mean?
Swapping the ring and pinion gears in your axles for a different ratio. On 4x4s it is usually done to a numerically higher ratio, such as 3.73 to 4.56, to win back the pull and engine revs that bigger tires take away.
Do I need to regear for 35s?
It isn't required: the truck will drive. From a 31.5-inch stock tire, 35s cost about 10% of the pull and revs in every gear. Light trucks with strong engines often live with it. Heavy, loaded or towing trucks, and small engines, are where regearing pays off.
3.73 vs 4.10: what's the difference?
4.10 turns the driveshaft 4.10 times for every turn of the wheels; 3.73 turns it 3.73 times. That makes 4.10 about 9.9% shorter: roughly 10% more pull at the tires and 10% more engine revs at the same speed in the same gear.
Is 3.73 OK for 35-inch tires?
From a 31.5-inch stock tire, 3.73s on 35s gear the truck like 3.36s on the original tires. Some trucks cope; many feel lazy on hills and the gearbox hunts between gears. Going back to stock gearing on 35s needs about 4.14, so 4.10 is the nearest common set.
Does regearing fix my speedometer?
It depends where your speedometer reads from. If it reads from the gearbox or transfer-case output shaft, regearing to the ratio that restores stock gearing largely corrects it. If it uses wheel-speed (ABS) sensors, regearing doesn't change it. Either way, many modern vehicles need the new tire size and axle ratio programmed in, for the speedometer and for the gearbox and stability systems.
Do both axles have to be regeared?
Yes, on a 4WD. In part-time 4WD, or full-time with the centre diff locked, the front and rear driveshafts are tied together, so different ratios make the axles fight and bind. In full-time 4WD with the centre diff open, a mismatch makes the centre diff slip all the time and wears it out. Both axles must have the same ratio, or as close as the factory pairs them (within a fraction of a percent).
Gearing figures are calculated from nominal tire heights. Updated 2026-11-14.