blowermax

Well I installed a 2013 jk non rubi front diff on my 07 without do any research...put it in 4wd and realized i couldn't go anywhere with 3.73 in the front and 4.10 in the rear....my ? is I am only going to be changing 1 set, so do I change the front to 4.10 or change the rears to 3.73's?? what the better choice...

JK505

I would go with 4.10's front and rear. Based on this:

2007 Unlimited
sprintex supercharger and 4WD this summer
16x8 7032 Pro-comps beaded with 35 ko2's
3.5 lift sitting on bilstein 5100's
TeraFlex Trac-bar...synergy HD Ball-joints
Fox SS with AEV geometry correction brackets
Pioneer Head Unit, Sub, Box and amp
Kicker speakers
LED's here and there

The 4.10's will turn the 35's better than the 3.73's, especially with the 3.8L. You'll notice a significant drop in "power" if you change the rears to 3.73. In the auto, you'll be going in and out of overdrive and gear searching. If you have a manual, you'll basically have a 5 speed because 6th gear won't turn the tires on any sort of incline. If you have an auto, you'll need to reprogram for the change in the gear ratio if you go 3.73 in the rear from your current 4.10.

You may be able to get away with 3.73s and 35's based on your elevation and how hilly/mountainous the terrain is where you live, but if you are halfway to 4.10s anyways, I would go that route and keep the 4.10's. I'm pretty sure you'll be glad you did.

GJeep

With your wheels, I'd definitely change the front to 4.1 .
It would also allow 35"s in the future, if you'll ever want this size.

JK505

I think he's already rolling on 35's based on his signature If so, you'll hate dropping to 3.73s after having 4.10s and 35's.

blowermax

@JK505 yes sir I am running 35's, I'm in socal so not many hills here...the 3.8 is gutless as it is...I have the Sprintex Supercharger still waiting to be installed but took advantage of the hyper tech programmer to account for the bigger tires...ok looks like 4.10's will be the way to go...Thank you very much guys!

blowermax

Ok, perfect...Thank you Sir!

blowermax

Ok so I called a rear end shop and they said Its not as simple as a ring and pinion going from a 3 series carrier to a 4 series carrier...is that right?

kfast24

If it's a Dana 30 front I believe the carrier changes. I'm not 100% but in the old Dana 30's you had to swap the carrier to get into the 4.10 gears or higher

blowermax

Thats along the lines of what they were saying, they are looking in thier books right now and going to give me a call back...

nthinuf

JK d30's with 3.21's have the odd sized carrier. A d30 with 3.73 will use the same carrier all the way up to 5.38's.

JK d44's use the same carrier from 3.21 to 5.38.

So, since neither of your axles are a JK d30 with 3.21's, you will not need a new carrier.

But, before you regear one end, have you considered just gearing both? There are about a gajillion threads on gearing. Very common recommendations for 3.8's on 35's are to go with 5.13 or 4.88 for auto's, and 4.88 or 4.56 for manuals. Put some consideration into this before spending money on 3.73's or 4.10's.

And, while the axles are torn apart is generally a good time to think about adding traction. And you may as well think about gussets/sleeves/truss. And ...