Ask The Expert- Preparing a 2014 JKU sport for 37's

MickeyB

Jeep Owner
My 2014 JKU sport is currently on 35's, 4.56 gears, 3.5" lift, 35 spline rear axle shaft, rear ARB air locker and gussets welded on the fronts. I want to make sure I am properly prepared to onto 37's, since the front still has a Dana 30. What all do I need to add to make sure that the 37's will do well on my rig?


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MickeyB

Jeep Owner
Mostly on road as a daily driver. I do go wheeling with friends about once a month but don't do anything crazy like Rubicon. Moab is on my list though. I'd like to be prepared if my interests change so I don't have to keep redoing things. By the way, I'm getting flat fenders next week too.


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Cloaked Willys

Jeep Fanatic
If you are doing lite wheeling and leave the front end uplocked and drive it smart by keeping leverage off the front end it can hold up. If you start to wheel harder I will recommend going to a D44 with a aftermarket housing.
 

Pthorpe84

Moderator
Staff member
Agreed with cloaked. With 37's the 44 would be fine locked, being it's a 30 I would leave it the way it is. 4:56 gears will be fine with 37's because you have 3.6. This will also keep you from blowing up the ring and pinion up front. Stay light on the skinny pedal and pick good lines and you will. Ever have a problem. I would go ahead and get a set of front chromoly shafts and swap them out.

Being that we all have jeeps on here...your interest will change and you will want to go bigger. You can easily pick up a front rubicon 44 for $2-3k pretty easily. Sometimes cheaper.

I would tell you to go ahead and get an extra set of ball joints because you will need to replace eventually. Not that you have to have it for 37's but drive shafts should be on your list as well. You may need some wheel spacers to handle possible rub when turning.


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timatoe

Jeep Fanatic
So I ran 35's on my basically stock D30 with 4.88's and an ARB for about 8 years, multiple trips to the Rubicon and to Moab and never broke anything. The downside to the D30 is the small pinion gear the deeper your gear set gets. I think you'd be fine with finesse.

Going to a 44 will provide you some peace of mind but not much more real world strength (in stock form) as they use the same axle shaft u-joints (well assuming JK's still do that). That being said I now have a full width 44 37's and two weeks ago blew a u-joint (Precision) and twisted a shaft on the Rubicon in an area that really non of that should've happened. I'd second getting the chrome moly shafts if it can be done cheap enough, otherwise I'd put that money toward a better upgraded axle. Make sure you run good Spicer u-joints too. (Although I've never broke a cheap AutoZone one)

I think in general it probably depends more on driving style than anything. I've seen guys run the Rubicon for years on 35's and completely stock D30/D35 combos (with lockers) and not break anything. I've also seen guys romp on it with D60/14b combos and break crap left and right.
 

Cloaked Willys

Jeep Fanatic
So I ran 35's on my basically stock D30 with 4.88's and an ARB for about 8 years, multiple trips to the Rubicon and to Moab and never broke anything. The downside to the D30 is the small pinion gear the deeper your gear set gets. I think you'd be fine with finesse.

Going to a 44 will provide you some peace of mind but not much more real world strength (in stock form) as they use the same axle shaft u-joints (well assuming JK's still do that). That being said I now have a full width 44 37's and two weeks ago blew a u-joint (Precision) and twisted a shaft on the Rubicon in an area that really non of that should've happened. I'd second getting the chrome moly shafts if it can be done cheap enough, otherwise I'd put that money toward a better upgraded axle. Make sure you run good Spicer u-joints too. (Although I've never broke a cheap AutoZone one)

I think in general it probably depends more on driving style than anything. I've seen guys run the Rubicon for years on 35's and completely stock D30/D35 combos (with lockers) and not break anything. I've also seen guys romp on it with D60/14b combos and break crap left and right.

LOL, Yeah. I might be guilty of this. The more you build up a rig the farther you can try to go.

If/When you decide to upgrade to a D44 I will recommend doing shafts and some of the normal other upgrades. If you order a complete aftermarket housing they will normally have them already installed and are ready to go. If you plan on going bigger than 37's be prepared to go bigger on the axles.
 

timatoe

Jeep Fanatic
If/When you decide to upgrade to a D44 I will recommend doing shafts and some of the normal other upgrades. If you order a complete aftermarket housing they will normally have them already installed and are ready to go. If you plan on going bigger than 37's be prepared to go bigger on the axles.
Yeah, seeing the mention of $2-3K for a Rubicon D44 (holy cow), I'd order a complete unit.
 

bOLsAK3

Jeep Newb
I'm also agreeing with cloaks post. It looks like you've got almost every angle already covered to add 37's comfortably.
 
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