The difference between a 3.73 vs 4.10 gear ratio can cause many questions for the automotive enthusiast. We at LMR.com provide the pros and cons of each option to help make up your mind about what best suits your driving style! Between these 2 different gears, a detailed guide has been provided to better help you understand what is more beneficial for your needs! The amount of performance you get for the surprisingly low-cost results is a very important upgrade that every Mustang enthusiast should take advantage of.
Which gear set you install in your rear axle can be a bit of a loaded question. It really depends on the kind of road speed you intend to do. For example, if you are more focused on top speed, acceleration, or if you do a lot of highway driving.
Use this rule of thumb: The shorter the gear ratio (higher number), the easier it will be for the vehicle to start moving and accelerating! This will, however, lower the top speed of the vehicle. Vice versa, if the gear ratio is taller (lower number) it has a slower acceleration but the top speed will increase.
Something noteworthy to consider, though it may feel like it, horsepower levels are not being increased by changing your axle gear ratio, just the torque. This is why performance ring and pinions are such a good and reasonably priced upgrade! You aren’t paying the higher price for horsepower increases, however, you are still getting the increased performance and decreased times at the track that increased torque can give you.
|3.73 Ratio||4.10 Ratio|
|Not as fast off of the line||Quicker Off The Line|
|Lower Torque||Higher Torque|
|Better Gas Mileage||Decreased Gas Mileage|
|Higher Top Speed||Lower Top Speed|
The way you can know which gear ratio you have is by counting the number of teeth on the ring gear divided by the number of teeth on the pinion gear. For example, if the ring gear has 37 teeth and the pinion gear has 9 teeth, the ratio is 4.11:1. So for every turn of the ring gear, the pinion will turn 4.11 times. Additionally, with a gear ratio of 3.73, the pinion will turn 3.73 times for one turn of the ring gears, and for a 4.10, the pinion will turn 4.10 times.
Another good visual way to understand this would be how many times your wheel spins compared to the rotations of the driveshaft. Jack up the rear of your Fox Body Mustang, SVT Cobra, or whichever vehicle you are working on and secure it on jack stands with wheel chocks around the front wheels.
Then, using blue painter’s tape, place a three-inch-long piece of tape on the very bottom of the driveshaft parallel to the vehicle. Next, you will want to place another three-inch piece of tape vertically on the sidewall of the driverside tire. These pieces of tape will help you count the number of revolutions (number of spins) for the driveshaft and the wheel. For every two revolutions of the wheel and tire, count the number of revolutions of the driveshaft. If the driveshaft spins roughly 2 ¾ times, that will equate to a 2.73 ring and pinion gear. If the driveshaft spins roughly 3 ½ times, that will equate to a 3.55 rear end gear. Likewise, if the driveshaft spins roughly 3 ¾ times, that will equal a 3.73 rear end gear, and if it spins just over 4 times, this will equate to a 4.10 rear end gear.
While it might seem like shorter gear ratios like a 4.10 gear is the way to go, you might also want to consider the following:
The higher the ratio, the higher the RPM at highway speeds. Not only will you accelerate faster, but it will also result in much higher RPMS while cruising and some may not want this to happen. Why does this happen? Because the gears are working harder to push out better performance so the extra power has to come from somewhere!
To keep it simple, if you want a daily driver and want to save a little on fuel and you care about performance but don’t want screaming RPM, then taller gears like the 3.73 ring and pinion are the way to go. On the other hand, if you don’t mind the loss in fuel mileage and higher RPMs on the highway, then we highly recommend a shorter gear ratio such as the 4.10 ring and pinion.
At that point, it is not about miles per gallon but smiles per gallon!