3.45 gears with 37" wheels??

[Jeep4Life]

Is this a bit much for stock gears and if so, where should this be bumped too? 4.11 or 4.88?

Thank you

 

[Brooks]

You'll want to go with the 4.88s. 4.11 will work, but not as well as the 4.88's with those tires.

 

[smritte]

4.88 minimum

 

[alex]

I'm running 4.88s on mine and have 37" tires. Now when I first got these gears, I had 35" tires. I might just jump to 5.13's one day.

 

[Ryan Frost Outdoors]

4.88's should do you well. Don't 5.13s kill the MPGs on freeway?

 

[smritte]

4.88's should do you well. Don't 5.13s kill the MPGs on freeway?

That depends on the vehicle and more specifically, the engine.

Changing gears puts the vehicle back in its designated power band. When choosing gears it shouldn't be random but should be done calculating the proper set. The larger tires change put our vehicles outside their power band. The size also causes more drag. Putting the vehicle back into its intended range may not be enough, sometimes you need to raise the RPM slightly to make up for drag. When I played with drag cars in my youth, you would calculate the gear ratio based on power band then calculate tire size to fine tune it.

Bottom line here is, gear ratio will help MPG by putting the vehicle back in its proper power range but, but can only help a little of the loss due to the extra weight we add and the extra drag from tires.

Another thing that needs consideration is pinion size and axle size. The lower the gear, the smaller the pinion and weaker the pinion gets. As you lower gears you also multiply torque. The larger tires strain axles as it is, adding more torque is fine as long as you don't over do it for the axle strength. The more splines an axle has, the larger the diameter and the stronger. To me, a 4.88-5.13 and a 37" tire are proper for most Jeeps and the limit for Dana 44's that are driven hard.

 

[Jeep4Life]

Thanks everyone. I'm scheduled in next week for 4.88's to get installed!

 

[TerraTamer]

4.88's should do you well. Don't 5.13s kill the MPGs on freeway?

Oh yeah it would. Those 4.88's are going to be golden for you.

 

[Fellow Traveler]

This guy from our 4x4 meet was running 4.11 with 37's for nearly a year and he finally just moved to the 4.88's and is loving the difference.

 

[WranglerGuy]

How did the install go, are you happy with the gears?