I have a ’07 JK Rubicon, 2 door. I lifted it with 3” Full Traction Ultimate Lift, Superior 4.88 gears, Tom Wood front & rear driveshafts and 35” Goodyear MT/R. I want to change to 37” tires to try to correct my RPMs that are running too high. My concern was clearance in the wheel well. A friend has a ’97 TJ and admits to knowing little about the newer jeep and since I only wanted an opinion on wheel clearance, I asked him for his opinion. He has not yet looked at the jeep, but this is what he told me in an email.
"What few people understand is that the parts on a Dana 30 that fail/have accelerated wear rates with 37" or larger tires are the exact (!) same parts that are used on a front Rubicon Dana 44 axle. The Rubicon's front Dana 44 uses the exact same axle tubes, u-joints, knuckles, ball joints, inner-C's, outer-C's, and outer axle stub shaft as a Dana 30. And it is those parts that aren't up to 37" or larger tires. The only parts that are different between a Rubicon front Dana 44 and TJ Dana 30 are the ring & pinion gears, center pumpkin (D44 housing), and inner axle shaft. Everything else is the exact same thing as a Dana 30.” Is this correct? I thought the JK had “beefier” axles than the TJ.

 

I believe this true for the front axel, but not the rear. I'm not 100% sure though about the rear axel.

 

I believe this was true for the TJ front 44. I do not believe it is true for the JK front 44. There is a recent magazine, either peterson or JP, with a complete article on the differences between axles including masurements

 

The front 'JK' D44 does share some parts with the front 'JK' D30. (different axles than the TJ's, though...) The D44 gears are huge in comparison to the 30, the rest can be handled with upgraded shafts, gussets - even a truss and/or sleeves if you want. Most here believe the Rubi D44 is fine for 37's. Very few think the D30 is capable to run them.

 

I am not 100% positive, but it is my understanding that statement was true for the D44 in the TJ. In the Jk the only similar parts are the outer C's and the tubes, everything else is heavier, tougher........

There is bound to be a member out there that can confirm deny and give us the 100% accurate answer.

 

+1. If you're going to run 37's on your rig-especially since you've got a locker-you'll probably want to beef up your stock Dana 44. Probably not needed if you're running on-road, but the first local guy here (that I know of) to bolt 27's onto his JK with a stock Rubi axle ended up with some pretty good carnage hwile wheeling...in an open meadow, in the snow.

 

I've read several posts indicating that snow eats axles, haven't seen the reasoning behind it though. Something I'll just have to research a bit

 

The problem with the 30 isn't the stuff it may share with the Rubi D44 - it's the puny ring and pinion.

Somebody refernced an article in a mag comparing Jeep axles. The article was in JP and rated the Rubi D44 as the best 44 ever. In fact it was the strongest non D60, or up axle.

The article can be found at:
jpmagazine.com/techarticles/154_0708_weakest_to_strongest_axles/index.html

 

What many people don't realize is the front axle in the JK is a much better axle than that of the TJ. I have 35's on my front 30 with no upgrades and I have not had any breakage and it has been wheeled hard a few times. Im not saying it wont break and I do plan on upgrading when it does! With a 2-door you have an advantage as well cuz you arent carrying as much weight as the 4-door. When I talked to my local 4wd shop they said the dana 44 isn't that much stronger than the 30 and I would be better off just upgrading the 30. Since you have 4.88's I would bet your 44's could handle 37's but just to be safe id get chromoly shafts and the C-gussets are pretty much a necessity. This is just mine and the 4wd shop's opinion though!

 

I don't understand your shops opinion. The real weakness with the 30 isn't the tubes, or axles or u-joints, it's the ring and pinion. You can sleeve, truss, and gusset all you want; you can upgrade the shafts and put CTM Ujoints in - but you still have the small gears. I was recently out with a buddy who spun the front gears in his LJ with 35's. He was open with no locker and had stock shafts.