Gear ratio for 35's on a 2015 JKU Rubicon 4 door

[coleman07]

I lifted my Jeep 4.5 inches and put 35's on it. I noticed that I don't get the engine braking I got with a stock vehicle, needing to use the brake on steeper declines.
Right now I am very hesitant to do a trail like Red Cone where I would need to brake instead of letting the engine get me down. On the other hand, I don't want to burn
up the engine on the interstate getting to the trail. I only use the Jeep to go off-road or get to the trail.

Using this website, https://go4x4it.com/wrangler-jk-rpm-calculator, I see that going to a 4.88 gear vs the 4.10 I have is an increase of 435 RPM at 70 MPH. Looking at this chart,



it appears that 4.88 is the right gear ratio but I want to be sure an increase of 480 RPM is ok at 70 MPH. Will the 4.88 offer the engine braking I desired when I was running a stock JK?

Thanks so much,

Sean

[xaza]

How are you coming up with an increase of 480 rpm? going 4.88 is an increase of 440 rpm versus the 4.1 on the 35" tire but what you want to do is maintain close to factory ratio. 4.1 gear on stock 32" tire was 2502 so only about 221 rpm increase which is quite minimal and honestly better because you have to account for the increased unsprung weight. I don't have a JK so I can't give personal experience but I would think 4.88 with 35" is good. It was perfect combo for my XJ.

[coleman07]

Thank you for the recommendation. Sounds like I know what I need. I was using this calculator on the Go4x4it site. With 4.10 and 35 in tire, they said the RPM at 70 MPH was 2288 and at 4.88, it was 2723 which is 435 RPM.

[Getaklu]

I run 5.13's with 315's (short 35's) and don't have a problem on the highway. Crawls well and lots of engine breaking. I was thinking that 4.88 was basically a wash with the bigger tire from the OE 4.10/tire combo when I was researching. I wanted to be a bit lower as I didn't like the OE ratio in 1st or reverse so went with the 5.13. IIRC, right around 3000 rpm at 75.

[coleman07]

Thanks for that info. i will look at 5.13 also!!

[Max]

I have 4.88 on my 37's and am happy.

[TNTJ05]

Did 4.56 on my 2door rubi JK on 35's, and 4.88 in a 4dr rubi JK on 37's. Both were great for street and trail with the 4:1 T-case.