4.88 or 5.13

[RandyCarol]

Hoping to be on 37's by the summer and will be regearing. My JK has the 3.6 and it's a 6 speed rubicon with 4.11 gears now. I've been doing a bunch of research and still can't decide. I still commute with it, that's why I'm even considering the 4.88's. I find 1st low really low with my current setup with 34's and wonder how it will be with 5.13's. Any suggestions for New England driving?

[Frank]

The best part of a Ruby is the 4x1 transfer case ratio ! People would kill for it . Are you satisfied with first gear in 2wd ? Having a rig balanced for both duty's is one of the toughest things . Look at a tire size Vs. gear ratio chart . Find the stock ratio with the stock tire size . The charts have a stock/power/economy rating. Look at the tire size you want to go with and what ratio they recommend to match the stock rpms . Then its up to you to go one or two ratios lower (Higher number) than that . The lower ratios are better suited to the off road side and higher ratios (lower number) better for economy and trips. You still have that 4x1 T-Case . Paying for a gear change is expensive , Research well before doing it. Post up in Tech and ask members with JKs and gear/tires you want what they run. it might help you decide. I have a 74 CJ-5 with a 4x1 T-case , 4.56 gears ,and 35s. I only have a 4 speed. I went from 3.73 with 32" tires to 4.56s and 35s and only gained 300 RPMs in 2wd ! I knew then that I should go with 4.88s but didnt and have kicked myself many times. Tough decision . Good luck FjR68

[RalphTomaccio]

[Hoodoo Man]

I wouldn't for a minute consider 5.13, for a JK the pinion head gets really small and delicate and can become a "fuse" or weak link offroad. Right now I have 3.73 and was running 35" MTR/K and the Jeep still drove fairly well with the Penstar and 6 speed. Didn't use 6th much except on the flat areas of the highway but handled the hills to and from Rausch with no major issues...

As you can see from the chart Ralph Posted the 4.10s are still in the 'Acceptable but "sluggish" range' with 37's... If you can find a "lighter" tire you may be able to save a few grand in re-gearing.... In the off season (now) I went back to my 33s and I was fairly happy with how the Jeep drove on 35s so I doubt I will re-gear anytime soon. The 33s still look good with my 2.5" Teraflex lift....

[RandyCarol]

Thanks for the chart and the advice. I only want to regear once. They will both be fine off road, 5.13 would be better if I ever went bigger but 37's on a 2 door seems plenty big enough. Most of what I read favors the 5.13 but my commute has no hills and if I wanted to put on a set of smaller winter tires the 4.88 would be better suited for that. I'll keep reading up on it, spring is still a ways off.

[RalphTomaccio]

I'm not as knowledgeable as most here, but I think I would go with the 4.88's based on that chart and the fact that it's a DD and no hills, FWIW.

[schwalby]

We went with 4.88s on our 2dr with 37s and street wise they have been great. Don't have any trail time yet with it and it isn't a Rubi but I think 4.88s will be fine for you.

[Frank]

Rubys come with 44 front and rear still ? That makes room for the pinion to be of healthy size . Only the D-30s suffered from pinion explosion . Still , just my opinion . FjR68

[MDSRACING398]

I have a set of 4.88 less than 1000 miles out of tj. If they fit jk your welcome to them Randy

[ASauer17]

I'm at 4.88 with 35s... My jeep drives completely different after. I'd stick at 4.88

[RandyCarol]

I have a set of 4.88 less than 1000 miles out of tj. If they fit jk your welcome to them Randy

Thanks Mark, but I think the JK went to a bigger pinion diameter. Thinking of going with beefier axles altogether.

It sounds like 4.88's are preferred for the type of wheeling/driving around here.

[Frank]

Theres no substitution for Cubic Inches or more gear ! FjR68

[Frank]

What did this Jeep come with for stock tire size ? If its 32s than your still going to be below stock RPMs. With a six speed trans. / I would seriously look at .13s or 38s and be closer to stock than the 88s. Just saying Dude , Its a tough decision and you gotta make it. FjR68

[RandyCarol]

32's with 4.11 stock, I have 34's now and it's fine until I get up into some hills.
According to Ralph's chart the 4.88 will put me back to stock and the 5.13 will get me a little lower than stock, so the 4.88 will give me a stock like ride and feel and the 5.13 will give me a little more oomph to compensate for the additional weight and rotating mass, which is good but they say it makes 1st gear in low useless for anything but technicial crawling, sometimes you need that wheel spin. I'm putting too much thought into this, it's only 130 RPM @ 70 MPH.

[RalphTomaccio]

I'm putting too much thought into this, . . .

I know exactly what you mean. Done this many times. You want a lot of information to be able to make a good decision and then you get so much information, you get "information overload", causing you to not being able to make any decision.

DD = 4.88's. There's your answer. Done!