What “3.73 gears” means—and why it matters

“3.73 gears” refers to a 3.73:1 final-drive (axle) ratio, meaning the driveshaft turns 3.73 times for every single rotation of the axle and wheels. In practice, this ratio delivers stronger off-the-line acceleration and better towing performance than a numerically lower ratio (e.g., 3.31), at the cost of slightly higher engine RPM at highway speeds.

What the number actually describes

An axle ratio expresses how many times the pinion (connected to the driveshaft) must turn to rotate the ring gear (and thus the wheels) once. With 3.73, the pinion rotates 3.73 times per wheel rotation. The ratio is set by the tooth counts of the ring and pinion gears—for example, a 41-tooth ring gear and 11-tooth pinion gear yield 41 ÷ 11 ≈ 3.73.

Where the ratio lives in different vehicles

On rear- or four-wheel-drive vehicles, the 3.73 ratio typically resides in the rear axle (and front axle on 4x4s). On front-wheel-drive cars, the “final drive” is inside the transaxle; the meaning is the same, though it isn’t in a separate differential housing.

How a 3.73 ratio changes the way a vehicle drives

The following points outline how a 3.73 axle ratio affects performance, drivability, and operating costs compared with numerically lower (e.g., 3.23–3.55) or higher (e.g., 4.10) ratios.

• Acceleration: More torque multiplication at the wheels improves launch and mid-range pull. Example: with 400 lb-ft engine torque and a 4.0:1 first gear, wheel torque is ~5,968 lb-ft with 3.73 vs ~5,296 lb-ft with 3.31—about a 13% gain.
• Towing and grades: Helps keep the engine in its power band, reduces “gear hunting,” and improves hill starts. Popular in trucks/SUVs spec’d for towing.
• Highway RPM and noise: At a given speed and top gear, engine RPM will be higher than with a 3.31 or 3.55, which can add a bit of cabin noise.
• Fuel economy: Slightly lower at steady highway speeds due to higher RPM, but can be similar or better in hilly terrain or when towing because the transmission downshifts less.
• Top speed: In many modern vehicles it’s unchanged (aero drag and power limit top speed), but gearing can move the speed at which the car reaches redline in a given gear.
• Transmission pairing: Overall ratio = transmission gear × final drive. A deep overdrive (e.g., 0.63–0.69) can offset higher axle ratios for relaxed cruising.

Put simply, 3.73 is a balanced “performance/towing” choice: quicker response and stronger pull, with a modest trade-off in highway RPM.

Quick math: RPM and speed

A handy estimate for cruise RPM is: RPM ≈ (mph × axle ratio × top-gear ratio × 336) ÷ tire diameter (inches). Example: at 70 mph with a 0.67 overdrive and 33-inch tires, 3.73 yields ~1,780 RPM, while 3.31 yields ~1,585 RPM—about a 200 RPM difference.

Where you’ll commonly see 3.73s

Carmakers often offer 3.31/3.55/3.73/4.10 options in trucks and performance-oriented SUVs and cars. The 3.73 sits in the sweet spot for towing packages and sporty trims, balancing acceleration and cruising comfort. Off-road packages may pair 3.73 with a low-range transfer case for extreme torque at low speeds.

How to find out if your vehicle has 3.73 gears

Several reliable methods can confirm your axle ratio without tearing anything apart.

• Axle tag or cover stamp: Many differentials have a metal tag or stamping listing the ratio (e.g., “3.73”).
• Door-jamb/VIN codes: Manufacturer axle codes or RPO codes can be decoded (e.g., GM GT4 = 3.73; Ford axle codes reference charts in the owner’s manual or online).
• Spin test: Safely lift the driven axle, mark the driveshaft and tire, rotate the tire once, and count how many times the driveshaft turns (≈3.7 turns indicates 3.73).
• Service records/build sheet: Dealer printouts or build sheets often list the final-drive ratio.

If you have a 4×4 or AWD, remember both axles must match; mismatched ratios can damage the drivetrain.

Considering a swap to 3.73s? Key points

Upgrading to 3.73 can dramatically improve drivability with larger tires or added towing, but it isn’t a trivial change.

• Cost and parts: Expect roughly $800–$2,000 per axle installed (parts, setup, bearings, seals); 4x4s require front and rear to match.
• Compatibility: Some axles have “carrier breaks,” requiring a different differential carrier for certain ratios.
• Calibration: Reprogram the speedometer/odometer and transmission shift points; some vehicles need ABS/traction control recalibration.
• Break-in and fluid: Light-throttle heat cycles for the first ~500 miles; change gear oil after the break-in to remove wear-in particles.
• Warranty and insurance: Modifications can affect coverage—check policies before proceeding.

Done correctly, a regear to 3.73 restores pep with larger tires and makes towing easier, while preserving reasonable highway manners.

Common misconceptions about 3.73 gears

These clarifications help separate gear-ratio fact from fiction.

• “Higher number = bigger physical gears.” Not exactly. It reflects tooth counts and leverage, not necessarily gear size.
• “It changes transmission gear spacing.” No—3.73 multiplies whatever transmission gear you’re in; it doesn’t alter the transmission’s internal ratios.
• “It increases engine power.” It doesn’t. It multiplies torque at the wheels, changing how the power is applied.
• “Fuel economy always drops.” Not always; in hilly regions or while towing, 3.73 can reduce downshifts and be as efficient—or more—than a tall ratio.
• “Limited-slip or lockers are part of the ratio.” Those are different features. You can have 3.73 with open, limited-slip, or locking differentials.

Understanding these nuances helps you choose a ratio for your needs without over- or under-estimating its impact.

Summary

“3.73 gears” means a 3.73:1 final-drive ratio: the driveshaft spins 3.73 times per wheel rotation. This gearing delivers stronger acceleration and towing performance and slightly higher cruising RPM than numerically lower ratios. It’s a popular, well-balanced choice for trucks, SUVs, and performance trims, and when paired with modern overdrive transmissions, it maintains comfortable highway manners. If you plan a swap, match both axles on 4x4s, recalibrate electronics, and observe proper break-in for reliable results.

Are 373 gears good for racing?

Yes, 3.73 gears are often good for racing because they provide a good balance of improved acceleration and reasonable top speed for many performance-oriented vehicles, but whether they are “good” depends on the specific vehicle, its powerband, transmission, and intended racing application. Higher gear ratios like 3.73 deliver more torque to the wheels for quicker launches, but they increase engine RPM at highway speeds, which can limit top speed and fuel economy compared to lower gear ratios.
 
Benefits for Racing

• Improved Acceleration: A higher number for the gear ratio (like 3.73) transfers more torque to the drive wheels, resulting in faster acceleration from a stop. 
• Faster Shifting: The improved acceleration can make the vehicle feel more punchy, and the gears will shift more quickly. 
• Good for Drag Racing: For drag strip racing or 1/4 mile runs, 3.73 gears are often suitable as they provide the necessary acceleration without running out of gear too early. 

Considerations

• Vehicle-Specific: Opens in new tabThe ideal gear ratio depends heavily on the vehicle’s engine powerband, vehicle weight, and tire size. 
• Balance of Acceleration and Top Speed: Opens in new tab3.73 gears are often considered an all-around compromise, offering a significant boost in acceleration over lower gears but with less top speed than lower ratios. 
• Engine RPM: Opens in new tabHigher RPMs are needed to maintain a certain speed, which can increase fuel consumption and potentially lead to higher oil temperatures. 
• Transmission Type: Opens in new tabA close-ratio transmission, common in manual cars, might experience too many shifts with 3.73 gears for some driving scenarios. 
• Type of Racing: Opens in new tabFor drag racing, 3.73 gears can be ideal. However, for road course racing or roll racing, a different ratio might be better depending on the car’s powerband and the length of the track, according to a Facebook post. 

What does 373 mean on the rear end?

And that is what gives you your rear end gear ratio. So you’ll see in here a little bit different terminology. You’ll see shorter gears uh which are also referred to as lower gears those are a

What are 3.73 gears good for?

3.73 gears are good for improving a vehicle’s acceleration and towing power by increasing low-end torque, making them a good option for off-the-line performance in sports cars or for heavy-duty towing in trucks. While they provide better acceleration than higher gears (lower number), 3.73s sacrifice some top-end speed and fuel economy compared to lower gears (higher number), such as 3.55 or 3.31. 
Benefits of 3.73 Gears

• Improved Acceleration: A higher numerical gear ratio like 3.73 provides more torque to the wheels, resulting in quicker acceleration from a standstill and a more “punchy” feel. 
• Better Towing Capacity: For trucks, 3.73 gears offer more pulling power and a mechanical advantage for moving heavy loads, making them ideal for towing. 
• Agile Performance: In sports cars or trucks, 3.73 gears can provide a more aggressive feel and improved handling in certain driving conditions. 

Considerations

• Reduced Fuel Economy: Because the engine needs to work harder to achieve the same road speed, fuel efficiency decreases with a higher numerical gear ratio. 
• Lower Top Speed: A 3.73 gear ratio will result in a lower overall top speed compared to vehicles with lower (numerically higher) gear ratios, as the engine reaches its RPM limit sooner. 
• Higher Engine RPMs: The engine will operate at higher RPMs at any given road speed, which also contributes to lower fuel mileage and can increase oil temperatures. 

In Summary
Choose 3.73 gears if your priority is enhanced acceleration, better towing capability, or a more spirited driving experience. If your primary goal is highway cruising and maximizing fuel economy, a numerically lower gear ratio, such as 3.55, would be a better choice.

What’s the best gear ratio for highway driving?

The best gear ratio for highway driving is a numerically lower ratio, such as 2.79, 3.00, 3.25, or 3.55, as these lower numbers result in lower engine RPMs at highway speeds, improving fuel economy and reducing engine wear. The ideal ratio depends on your vehicle, transmission, and driving goals, so a specific calculation using your tire size and RPMs is recommended.
 
Understanding Gear Ratios

• Numerically Lower Ratios (e.g., 2.79, 3.25): These are considered “taller” or “higher top-speed” gears. 
  • Pros: Better fuel economy on the highway, lower engine RPMs, and increased top speed. 
  • Cons: Slower acceleration and less torque for heavy loads. 
• Numerically Higher Ratios (e.g., 3.91, 4.10): These are considered “shorter” or “lower top-speed” gears. 
  • Pros: Faster acceleration, more torque for towing, and better performance in city driving. 
  • Cons: Higher engine RPMs at highway speeds, which negatively impacts fuel economy. 

Key Factors to Consider

• Vehicle Type: Different vehicles are designed for different purposes. For example, a heavy-duty truck will have different ideal ratios than a sporty car. 
• Transmission Type: Transmissions with overdrive gears, especially those with double overdrive, provide lower engine RPMs on the highway, allowing for taller gears to be used effectively. 
• Tire Size: Taller tires (larger diameter) will lower your engine’s RPM at a given speed, and you may need to adjust your gear ratio accordingly to compensate. 
• Driving Purpose: Your main goal will determine the best ratio. 
  • Highway Cruising/Fuel Economy: Choose a lower numerical gear ratio. 
  • Acceleration/Heavy Towing: Choose a higher numerical gear ratio. 

How to Calculate Your Ideal Ratio

1. Find Your Current Gear Ratio: Determine your vehicle’s existing final drive ratio. 
2. Determine Tire Size: Measure your tire’s diameter. 
3. Calculate Engine RPM at Highway Speed: Use a formula like: 
   • RPM = (MPH x Gear Ratio x 336) / Tire Diameter 
4. Adjust Based on Goals: Use the calculated RPM to adjust your gear ratio. A lower RPM for highway driving is generally better, but you’ll sacrifice some acceleration.