This is the most frequently asked question after re-gearing my Jeep “what gear ratio should I opt for – 4.88 or 5.13 ? can 35″ or 37” tires be used with a stock gear ratio? This article aims to provide clarity on the matter.
Gear Ratio Relating to Vehicles
The gear ratio represents the relative speed between the driven gear and the drive gear in a vehicle’s transmission. These gears are used to manage the transfer of power from the engine to the wheels.
The transmission and axle in your vehicle were chosen based on the specifications at the time of purchase, which determine its acceleration, top speed, RPM, and towing capacity. Gear ratio have an impact on fuel efficiency, torque, and transmission shifting. Installing larger tires like 35″ or 37″ can alter the balance.
Gear Basics | understanding gear ratio
The gear ratio indicates the number of teeth on your ring and pinion gears and it shows how many times the driveshaft has to rotate to make the wheels complete one revolution. For example, a Jeep with a gear ratio of 4.10 requires the driveshaft to rotate 4 times for the wheels to spin once.
To Simplify GEAR RATIO even further
Lower gear ratios result in slower speeds but greater acceleration. Conversely, higher gear ratios and larger tires lead to less acceleration. Short gear ratios are ideal for off-roading activities like rock crawling, but have a negative impact on fuel efficiency.
Re-GEaring BENEFITS: OVERLANDING/TOWING
The task of transporting heavy gear and equipment, including towing, while overlanding, especially on rough terrain, can place a substantial burden on your vehicle’s engine and gears. Re-gearing helps balance engine power and tire speed by providing additional torque to the wheels, making it easier for the engine to move the load and decrease the likelihood of breakdowns.
Additionally, re-gearing can also improve the overall driving experience during overlanding trips. With the correct gear ratio, the vehicle will have improved control and handling, making it easier to navigate through challenging terrain.
Gear Ratio and Vehicle Purpose
Before changing the gear ratio, it is important to find the optimal gear setup for your 4WD. This involves taking into account the use of the vehicle (daily transportation, all-terrain adventures, or specialized off-road) and the type of vehicle and transmission (manual or automatic). These considerations will help you determine the ideal gear ratio.
As an example, my 2018 Jeep JK with an automatic transmission is designed for full-time off-road adventures such as rock crawling, and has a gear ratio of 5.13 for its 37″ tires. On the other hand, my friend Josh’s (TAKJEEP) 2021 Jeep JL with a manual transmission is an all-purpose vehicle for daily driving and off-road with 37″ tires has a gear ratio of 4.88. This is really depends on your purpose and off-roading goals.
jEEP wRANGLER geAR rATIO cHART, 3.6 pENTASTAR
What should be your new gear ratio for improved fuel efficiency and enhanced performance?
(Old Gear Ratio) x (New Tire Size) / (Old Tire Size) = New Gear Ratio
4×4 Calculator Menu (Gear Ratio Calculator Online)
Preparation for Re-Gearing
In addition to online research, consider joining Facebook groups or forums related to your off-road vehicle and contacting local off-road shops for advice and recommendations. As off-roading and overlanding gain popularity, securing appointments may become more challenging.
Utilize this waiting time to plan and ponder upgrades, such as installing trusses and lockers, which will ultimately save you money on labor costs. Remember that both front and rear axles should be re-geared simultaneously to avoid any issues.
COST OF RE-GEARING MY 2018 JEEP JK TO 5.13 WITH ADDITIONAL UPGRADES
WHAT ARE THE NEXT STEPS AFTER RE-GEARING?
Breaking in your new gears is typically necessary, following the guidelines from the shop and installers. This may involve driving 500-1,000 miles on regular roads before off-roading.
Be sure to inquire about the warranty and what to do if you notice any small fluid leaks in the first few hundred miles, as this is normal. If the leaks persist, you should contact the shop to have the vehicle inspected to ensure the axle seals are not damaged. It is advised to buy a tuner or programmer if you do not have one already. The tuner will adjust your speedometer’s tire size readings and shift points.
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The installation of larger tires and the transportation of heavy loads of equipment can put pressure on your vehicle’s engine and gears. Re-gearing can enhance safety, as well as the driver’s enjoyment of the trip, by giving them more confidence in the vehicle’s ability to handle challenging conditions. Additionally, re-gearing can improve fuel efficiency by reducing engine wear and tear and lowering RPM, thus conserving fuel.
