silverbullet88

Right. The 4-1 rubicon case is sweet and still works well with my setup. What do you mean the other gears though? In 2wd?

I just always imagined re gearing and it holding 4th.

jchappies

Awesome calculator for Jeep

Gear Ratio RPM Chart Calculator

Mike H.

go to this website Gear Ratio Calculator
in 1 column enter 4.10's, in the other enter 5.13's and compare the 2 side by side.
I used 42RLE for transmission, NVG241or for t-case and 33.75" tire for 35's.
With 5.13's, in 3rd gear, 60mph you're going to be sitting at ~3050rpms, 70mph will be at ~3600rpms.
With 4.10's, in 3rd gear, 60mph you're going to be sitting at ~2450rpms, 70mph will be at ~2850rpms.
You say it is dropping into 2nd gear now... sooo...
With 4.10's, in 2rd gear, 60mph you're going to be sitting at ~3850rpms, 70mph will be at ~4500rpms.

Since under load the 3.8 is going to work best between 3500-4500rpm (TQ peak)...
I'm betting that you will go up moderate/typical grades in 3rd at 70mph with 5.13's(3600rpm) that currently with with 4.10's will be asking for 2nd gear to do 60mph(3850rpms). I'm also betting it will go up lots of slight grades in 4th at 2400rpm where currently it's looking for 3rd and 2850rpms.

Good luck.

silverbullet88

Thanks that's a lot of good info. Exactly what I was thinking it would be around. So why re-gear? You'll get 4th back for the most part but that's about it. And some low end acceleration. If the torque converter can lock in 3rd or 4th and keep the heat down.

I just need more HP!!!!

TheDirtman

any time you go up a steep hill your transmission is going to shift into a lower gear. With your current set up I would just leave it but if you go to an actual 35"+ tire a re-gear should be considered. Not having proper gears puts stress on the entire drivetrain including the driveshafts.

silverbullet88

Yeah that's a good point. 35" that actually measure that while mounted?

TheDirtman

Yes, I try and use actual size since it varies so much between different manufacturers.

Wandell

I know ours drives much better with overdrive off running 35's and 3.73 gears. I'm sure not as good as with lower gears, but much better than with overdrive on.

silverbullet88

Yeah. It's just a dog. Before I put anymore money into the 2dr I'm going to wait to see what the jl is like. If I don't like that then a 4 door jk it will be.

Either way it'll be a 6 speed

GunDude

3.73's and O.D off was ok. But, ended up regearing to 5.13's, because I wanted Trutrac's front and rear. If, it is power you want, then drop coin on a V8 and not another dog. Glad, I do not live where there are big mountains!