What gear ratio for 37s?

[galvard19]

I have a JK 2016 Sport unlimited and have a 3.21 stock gear ratio, I'm not sure what I should change it to, but right now its too sluggish. I currently have 37" Tires with 20" rims. I don't do much climbing, but a lot of people have told me different things from re-gearing to 4.11 to 4.56 to 4.88. I know that over 5 is too much for what I do and the cost is basically the same for the other ratios to change-out. Does anyone have a recommendation and a legitimate reason why they choose that ratio?

 

[conky]

My 18 Sahara JKU came with 3.21 gears and 35s. It's a sluggish turd on any incline over 30 mph. I dont see how you are doing it with 37s. I notice it more when I have the back of the jeep loaded and all the family with me. I'm definitely going to change gears to at least 4.11 but considering 4.56. I would think with 37s you would need at least 4.56 minimum. Only thing though, I think that if you go past 4.11 you'll also need to change the carrier out as well.

 

[Mattznpc]

My 18 Sahara JKU came with 3.21 gears and 35s. It's a sluggish turd on any incline over 30 mph. I dont see how you are doing it with 37s. I notice it more when I have the back of the jeep loaded and all the family with me. I'm definitely going to change gears to at least 4.11 but considering 4.56. I would think with 37s you would need at least 4.56 minimum. Only thing though, I think that if you go past 4.11 you'll also need to change the carrier out as well.

View attachment 115301

On my 2011 jk I had 373 stock gears and now running 37" tires with 488 gears. Seems to be a perfect combo for me

 

[Chris]

If it's a manual I would gear it to 4.57, if it's an auto, 4.88.

That is my recommendation for a 3.6 JK with 37s.

 

[Willys14jk]

I run 4.56 on 35x12.50x15. The weight of the tire is almost the same as a 37x12.50x17 so it should in theory be similar. I get 17-18 on the highway 15-16 in town. 4.88 is going to give you a big more low end grunt but higher rpm up top. I'm at about 3k at 70 mph which isnt terrible in 6th gear. All depends on how much you care about mileage.

 

[Ballermaris]

I have a JK 2016 Sport unlimited and have a 3.21 stock gear ratio, I'm not sure what I should change it to, but right now its too sluggish. I currently have 37" Tires with 20" rims. I don't do much climbing, but a lot of people have told me different things from re-gearing to 4.11 to 4.56 to 4.88. I know that over 5 is too much for what I do and the cost is basically the same for the other ratios to change-out. Does anyone have a recommendation and a legitimate reason why they choose that ratio?

I have 35's on my JK. When I decided to upgrade, I went all the way with full electric locker diff's front and rear. I used 4.56 gearing and had the work done at my local 4WP store in Norcross, Georgia which took about 2 days to complete.

An advantage over the mechanical lockers is you have full control and can engage them on-demand as needed. The activation switches have a safety interlock to prevent accidental activation. (You can find a photo of them that I have here on the forum.)

Since I do tow a travel trailer with the JK, it just made sense to make the changes.

As for your taller tires, you will need to have the speedo recalibrated to reflect the taller tires so that mileage is recorded more accurately, and to prevent the local police and state troopers from having a field day with you with speeding. You are going faster than you think since the taller tires are running now.

With the 4.56 and the 35's I turn about 2500RPM at 65, and 2550-2600 at 70 MPH. If pulling the trailer, I run around 62 MPH, pulling around 2250-2350 RPM.

The 4.56s are good for general driving and of course, pulling the trailer.

Let's face it, the Wrangler is NOT a speed demon. I have no interest in doing 185 MPH, (the tires in the first place would never survive) and frankly, the Wrangler is meant for exploring and going slow about your business. So if you see something, you can stop, have fun, and perhaps learn some interesting history.