viking

I waited till I put in a prorock 44 front with 5:13 gears and lockers front and back. That is a big step up in size and money.

JPop

If your OD is off, you are essentially running 5.38s at cruise speeds with the 3.73s. A little steep for cruising on the freeway, but certainly not out of bounds. If that feels appropriate at highway speeds, you should look toward the numerically highest gear set, although if 5.38s are available for a D30 I would have grave concerns about durability.

If your driving 60mph on the interstate, 4.88s would be fine. At 70mph anything more than a 2 degree grade and you are going to unlock the converter and have a kick down in gear. If you're unsure of the grade of your overpasses, you can get plenty of smart phone inclinometers for 99¢ or get one at your local 4x4 store for $12-15. If you're cruising at 75+mph 4.88s and 37s aren't going to work for you. Any grade or headwind is going to cause a kick down, robbing you of efficiency and placing undue strain on the drivetrain.

From my vantage point, 5.13s are the way to go. Only you know the way you drive and your expected level of performance. You can certainly make 4.88s work for you with conservative freeway speeds and flat terrain. That's not the path of most, and the minimal savings of dropping less than 200 rpm aren't going to provide much if any efficiency difference, especially if you have a greater frequency of kick downs.

datuna13

I've been running 37's with 5.38 Yukon Gears and it drives great! But I have a Rubi

CJ7nvrstk

What's that old saying?

If you can't dazzle them with brilliance, baffle them with BS.

Just trying to help a brother not make the same mistake I did my listening to the "experts" telling me 5.13s and 37s>

Mebee I should include that in my sig.

Back on topic, Tires first.

JPop

Please enlighten us as to how 5.13s were a mistake? Was it that the extra 5% of rpms had a huge detriment on efficiency? Is it that you just don't need that much gear because you're cruising on the freeway at a speed below 70mph? What gives?

You offered to take me for a ride the next time I was in the Fort Worth area to demonstrate that you didn't kick down at 60 or 65mph. Not the same as driving at 70mph as the aero drag is what requires exponentially more power (50% more power to drive 70 than 60mph). The charts in the FAQ are set up for 70mph as it's a typical posted speed for our interstates. If you never drive that fast, all the data the charts contain doesn't do you any good. When I had my 3.73s and 35s I could roll down the NC coast in 6th gear at 35mph, but I couldn't go 70mph in 6th over an overpass without slowing down. So there are lots of factors in play and it's certainly far beyond the box of your flatland lower mph personal experience.

CJ7nvrstk

As you say in this thread JPop, it's not a one size fits all. If you would actually read what I post instead of being so insistent on arguing with me and trying to prove me wrong you would see that I have explained it multiple times. Why explain it to you again when you have been unable to comprehend my explanation the half dozen times I have explained it? Sorry if you can't grasp that but I will not explain myself to you again when I have already done so.

So like you said, it's not a one size fits all.

GOBIGRED

Sorry to butt in but i have been strugling with this regear thing for a month now. I just need some help. I have a 2011 JKU with 35's and an automatic. I live in nebraska this vehicle is a DD with interstate speeds of 70-80 mph. I will be off road at least 2 times a week. fuel consumption is not an issue to me. I will go to 37's when 35's are worn. my local 4x4 shop suggested 4.88 he said 5.13 gears can be week in a d30 would like any and all info. People with real life expierence would be nice not so much what you've read or heard some where. Thanks

blueice

I live in the Seattle area with many hills and big mountains nearby we trail run. My rig is a 2010 JKUR with 37" MT/R (true 36+ tire) and 5.13s. It does okay on the interstate but my buddies similar rig with 5.38s is definitely better at these speeds. Off road no problem as the 4:1 transfer case seems to do just fine and I crawl up some very steep trails and heavy rocks. I temporarily borrowed some 37" Toyos and wow did that extra mass make it sluggish. I debated 5.13 vs 5.38 but was concerned about D44 5.38 ring strength in rocks and shearing teeth like what has happened to Eddie's crew a few times. Compromises and dilemma. I am happy with 5.13 since no breakage yet and I'm cool with slowing down on grades, after all it is a Jeep

CJ7nvrstk

When you are using fuzzy math, that so called "math and science" is exactly that.

I have given examples and been soundly ignored. I have presented facts and been told that the designers and builders don't know anything and that board members here are more knowledgable than the design teams that designed and built our jeeps. I have been argued with just for the sake of arguing because you think that you can beat me into submission and make me agree with your bad advice. Yet you will be suspisiously absent from certain posts that don't agree with your line of thinking.

https://www.jk-forum.com/forums/show...d-32-s-or-33-s

So, am done here trying to explain things to people who won't listen.

A mind is like a parachute, it doesn't work if it's not open.

roketman

I had Mickey Thompson Baja Claws mounted on Spyderlocks. They weighed a ton. I had 35s when i regeared and 5.13s were great. with the 37s, no power and gas mileage was terrible. I was advised not to put 5.38s in a dana 44, really need a d60.