Adding large diameter 37-inch tires and lift is common on Chevy Silverado to get better ground clearance for off-road applications. However, it results in problems like loss of power, reduced fuel economy, and poor gear shifting in automatic transmissions.
4.56 is the best gear ratio to use with 37-inch tires on Chevy Silverado pickup trucks. It will ensure optimal performance with the best fuel economy and reduce maintenance issues. The rule of thumb is to increase the stock gear ratio by the percentage you have increased the diameter of tires. You can use gear charts to find the suitable gear ratio according to tire diameter and engine rpm.
I have explained other options to improve the power loss due to using larger-diameter tires on your truck. You will also find the benefits of regearing the axle after a change in tire size.
What gear ratio is best for 37-inch tires on Silverado?
The axle gear ratio defines the number of driveshaft revolutions when the wheel completes a rotation.
Therefore, a bigger gear ratio means smaller gears and more engine revolutions per minute (rpm). For example, 4.56 is the best axle gear ratio for a Chevy Silverado pickup truck with bigger 37-inch tires.
Adding bigger than stock tires adds extra weight and increases wind friction on your pickup truck due to increased vehicle height.
Moreover, the effective distance between the axle center point and the ground increases. Therefore, the engine has to exert more force and torque to ensure sufficient traction and road grip.
You can overcome this side effect of larger tires by increasing the gear ratio or using smaller gears. There are specific formulas and gear ratio charts to determine the best option for you according to the tire size selected and spacers added to increase height.
For example, 4.56 is the optimum ratio if you choose the 37-inch tires on Silverado. You can go for higher axle ratios like 4.88 or 5.13 to get maximum power to turn the bigger tires, but too small gears can become weak points in the drivetrain, resulting in damage.
Why do I need to regear my Silverado for 37-inch tires?
Chevy Silverado pickup truck has an optimum drive ratio based on its installed transmission and axle gear ratio.
As a result, it has efficient fuel economy, other performance indicators like power and torque, and engine rpm at the designed drive ratio.
However, selecting larger 37-inch tires requires the engine to exert more force to move the vehicle.
Therefore, it increases fuel economy and loss of power and torque. You will observe these effects more clearly when your pickup truck needs power, like towing, climbing, or snow plowing applications.
Moreover, it puts the engine and drivetrain under stress causing maintenance issues in the future. 37-inch tires also have more weight and height than stock ones.
Therefore, you may lose a small portion of engine power to overcome increased weight and wind resistance.
You can overcome these problems by increasing the gear ratio to match the design drive ratio. It sums up the requirements for regearing the axle ratio of your pickup truck whenever you choose bigger tires.
How can we compensate for the gear ratio problem due to larger tires?
There are some methods to overcome power losses and reduced fuel economy due to drive ratio imbalance caused by bigger tires.
One of the practical yet expensive methods is to swap the truck engine with a powerful one. With increased power and torque rating can have better performance with larger tires.
You can also go for a supercharger installation to overcome the problems caused by the gear ratio mismatch for 37-inch tires on Chevy Silverado.
However, both of these options are expensive and time taking. One simple yet cost-effective solution is to swap the ring and pinion gears with new ones according to the calculated ratio.
Does increasing power resolve the Silverado gear ratio problem with 37-inch tires?
You can increase the engine’s power to compensate for the power loss due to larger diameter tires. However, it will be effective only if you select sizes closer to stock tires for your Silverado.
If you replace the bigger tires, like 37 or 40 inches, this solution will not work. Moreover, it will not correct the drive ratio mismatch problem.
It will not relieve the stress on the drivetrain and transmission, reducing its service life and durability.
Gear shifting on the automatic transmission will not be according to designer settings due to the rpm change.
Therefore, a basic power upgrade, not less than an engine swap or use of a supercharger, will not be feasible to compensate for the gear ratio problem and improve the driveability of your truck.
How to find the best gear ratio for Silverado pickup trucks with larger tires?
There are specific formulas, good practices, and gear ratio charts to determine the best one for Chevy Silverado.
A general rule of thumb is to increase the gear ratio by the percentage, as is the increase in the diameter of the tires.
For example, if you replace the 30-inch tire with a 37-inch, there is an increase of 23% in diameter. Increase the stock gear ratio by 23% and find its closest one to compensate for the drive ratio.
Gearing charts are available, representing the optimal engine rpm for each axle gear ratio and tire size.
You can choose the best one by matching these values from the charts. Although choosing higher ratios for off-road, climbing, or hauling heavy load applications seems lucrative, it reduces the size of pinion gear on the axle.
Making it too small can reduce its size, causing it to break easily. Therefore, you should choose the right one according to the chart or ratio formula we have already discussed.
What are the benefits of gear ratio change with 37-inch tires on Silverado?
Having the best gear ratio with bigger 37-inch tires has plenty of benefits. It compensates for the power loss and also improves fuel economy in your Silverado.
It will correct the engine rpm change and the speedometer reading on your truck. Furthermore, it will also restore the shift points for automatic transmissions and work smoothly.
Other benefits are improved driveability with an effective response to throttle and acceleration. Biggest of all, it will reduce maintenance issues relieving stress on drivetrain components.
It will also enhance the off-roading experience of the pickup truck in rough terrains like dirt or mountains.