One of the downsides of lifting your vehicle and adding larger tires is a loss in performance. Rotating all that extra mass requires more power. The easiest way to gain some of that performance back is to swap to a numerically higher gear ratio.
Why did we say it that way?
Ratios are an interesting phenomenon. The higher the number the lower the gearing. @#$@#$?
Gear ratio works like this. Our original gear set was listed a 4.10. That means for every revolution of the tire the driveshaft rotated 4.1 times. If you want to properly write out gear ratios it should look like this. (4.10:1) In this manner, we can multiply the force created by a vehicle’s engine making it more efficient at doing a task.
There are other factors like transmission gearing that also affect the final drive ratio. In this case, we are going to focus only on the tires and the ring and pinion to keep it simple.
Larger tires need more gear ratio.
More weight and a larger diameter take more initial torque to get rolling. They also travel further per revolution reducing engine RPM at highway speeds. All of these factors contribute to reduced performance and often less fuel economy from your vehicle.
I covered this previously “What the Diff – Gear Ratio”. The goal with the swap was to get the engine RPM back to near stock and return some driveability to the Jeep.
There are a few gear swap calculators out there. Most are based on a 1:1 final drive ration in the transmission. For a Wrangler that’s 5th gear. That takes the transmission multiplication or overdrive out of the equation.
For me, I wanted to get back to the same overall ratio I had from the factory. That meant swapping to a 4.88:1 ring and pinion.
What’s it like?
Jeep’s are always fun to drive. They are more fun when they can get out of their own way. I didn’t realize how much acceleration and 6th gear performance I had given up until I got it back. It’s exceptionally nice to be able to accelerate in top gear and not have to downshift on small grades. Stay tuned for some performance testing. I will be comparing our G-Tech tested power and acceleration from prior to the gear swap to the new setup.
Once again thanks to Rick at RnR Auto and Off-Road for his help!