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Discussion Starter · #1 ·

I'm new to this site and am glad to see that it specializes in all types of JK's. I'd like to tap you JK Sahara owners for info on adding 37 tires. I was informed that the Rubicon can handle 37 tires offroading without a problem, but can the Sahara do the same with out having to change the axels or having problems later?

 

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I have heard that the JK D30 is closer to the strength of the older D44's. Not sure about that, but if true, then you should at least be safe with 35's. 37's may be pushing it...Really not sure. An equally legitimate concern, should be the type of wheeling you intend to do. If you plan to wheel it often and hard, then most vehicles are gonna eventually see some kind of breakage. If your plans are going to be dirt/ fire roads/ mud, and only the occasional hardcore venue, then you will be a lot more likely to ward off significant failure. Still surprises me what some older TJ's with bone stock D30's can do with a set of 35's (again...Not that they are doing crazy stuff every weekend). JMO
 

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Depends on how heavy your foot is off road really. CJ/YJ/TJ guys have gotten away with 37s for years on those versions of D30s. Some with mods, some not. Just depends on how hard you beat on it.
 

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I don't see why not I believe and could be wrong but I think the front axle is now the same minus a locker
The Sahara comes with a D30 front, and can't even be ordered with a rear locker as an option like the X version can.

The ONLY JK that can be ordered with a front D44 is the Rubicon.

You CAN order the F/R D44's with lockers and 4.10 ratios separately from Mopar though...but, if you wanted a front D44, and were buying a new JK, it would make more sense to just order a Rubicon at that point.

That said, the new HD D30's are probably strong enough to wheel 37's as discussed, as long as you are not too yee ha on the skinny pedal. Smooth drivers can regularly get away with that, not so smooth drivers will even break D44's with 31's....etc.

The gearing is also an issue....as going from a Sahara's std 32's to 37's will DROP your rpm about 13.5%....and a Sahara's stock gearing is 3.21....

...the Rubi's stock gearing is 4.10.

Going from 3.21's to 4.10's RAISES your rpm by ~ 28%

In other words...a 4.10 Rubi running 37's is STILL effectively geared lower than a 3.21 Sahara running 32's.

:D

I'd like to point out that running 37's involves a crossing over in rolling resistance....35's don't make an enormous difference over the stock 32's, but 37's DO....so that extra gearing is doing a lot of extra work as well...which is why many re-gear for 37's, but most do not for 35's (Some want to re-gear period, of course, as lower is better off road, etc...)

Food for thought.
 

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The Sahara comes with a D30 front, and can't even be ordered with a rear locker as an option like the X version can.

The ONLY JK that can be ordered with a front D44 is the Rubicon.

You CAN order the F/R D44's with lockers and 4.10 ratios separately from Mopar though...but, if you wanted a front D44, and were buying a new JK, it would make more sense to just order a Rubicon at that point.

That said, the new HD D30's are probably strong enough to wheel 37's as discussed, as long as you are not too yee ha on the skinny pedal. Smooth drivers can regularly get away with that, not so smooth drivers will even break D44's with 31's....etc.

The gearing is also an issue....as going from a Sahara's std 32's to 37's will DROP your rpm about 13.5%....and a Sahara's stock gearing is 3.21....

...the Rubi's stock gearing is 4.10.

Going from 3.21's to 4.10's RAISES your rpm by ~ 28%

In other words...a 4.10 Rubi running 37's is STILL effectively geared lower than a 3.21 Sahara running 32's.

:D

I'd like to point out that running 37's involves a crossing over in rolling resistance....35's don't make an enormous difference over the stock 32's, but 37's DO....so that extra gearing is doing a lot of extra work as well...which is why many re-gear for 37's, but most do not for 35's (Some want to re-gear period, of course, as lower is better off road, etc...)

Food for thought.
Yeah I figured out he had a d30 but was unaware that you couldn't get the sahara with a front 44. Not sure what I was thinking, at one time did the sahara's and x's come with an upgrade for the rear (d44) vs d35 or some thing.
 

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My 2 cents...

Been wheeling a front D30 and 37s for about a year now. So far - so good. Most of my wheeling is mud, water, sand, and forest roads. Very rare that I find myself climbing anything - not that I dont enjoy it - this is Florida. I am very conservative w/ the skinny peddle and I am sure that helps.

edit: I should note that I do wheel a LOT compared to most of the jeepers I talk to. I try to get out at least every other weekend and every weekend in the fall/winter/spring.

Something to consider: how wide of a tire are you planning on running? So far the only two axles that I know of around here that broke running 37s were on Rubicons w/ front 44s. And they both had pretty wide tires. Correct me if I am wrong (and I am sure someone will), but the wider the tire the more resistance - no?

All that said, I just priced a Mopar D44 w/ 5.13 gears and locker the other day as my tastes are starting to change from typical florida wheeling to rocks and climbing. That and I plan on going to Texas next Fall.

But yeah, you can get away w/ 37s and a front D30 if you're not too wild.

edit: nice to see you here Rick. Glad you found the place.
 

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Yeah I figured out he had a d30 but was unaware that you couldn't get the sahara with a front 44. Not sure what I was thinking, at one time did the sahara's and x's come with an upgrade for the rear (d44) vs d35 or some thing.
Yeah....WAAAY back, the D35 REAR was std...and the D44 REAR option existed...but the FRONT axles were ALWAYS D30's except for the Rubicon.

The assumption by Jeep was that the Sahara was NOT going to be off roaded, and was the street cruiser version.

Thats one of the reasons why you can add a rear locker and edisco to an X model, but not a Sahara, etc.

When the TJ's came out, it was not like that, and the Sahara's had wider stock fender flares and the same off road options as the other TJ's....but DID come with more luxo boat stuff std.

:D
 

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My 2 cents...


So far the only two axles that I know of around here that broke running 37s were on Rubicons w/ front 44s. And they both had pretty wide tires. Correct me if I am wrong (and I am sure someone will), but the wider the tire the more resistance - no?

.


The wider tire will add more stress for sure. The more likely cause of the broken D44 would be running it locked. Turning the front locker on can give great traction to a point but there is a LOT of stress put on the front u-joints and internal components when both shafts are locked together. Any degree of steering angle will add stress and often break u-joints which then takes shafts out with it.

You will find that many new Jeepers like to turn on the lockers and leave them on and do whatever the hell they want. This is VERY VERY hard on the axles. Lockers really should only be used when you need them to get past an obstical, get unstuck etc and then TURN THEM OFF. They also should not be used when the wheels are cranked all the way to one side. The bind this creates in the u-joint will pop them almost instantly.

You will easily see more broken front axles with lockers than ones without.

The weakest point is mostly the u-joints. (which should be the same size on these D30 or D440. The entire housing is the same except for the center section and the size of the gears inside. (which are rarely broken under normal wheeling).
 

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Here is a little food for thought. I wheeled this TJ with a D30. (low pinion, so not as strong as the JK high pinion, plus smaller u-joints) for 10 years and 160K and never broke it. Here is some photo evidence of what you can do with a d30 front. I ranged from 33s to 37 with steel beadlocks on the Jeep.




 

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Discussion Starter · #14 ·
The first series of 2007 production on the Sahara came with D44 rear and 4.10 gear... I believe that 08+ is being made with D35... Being in Florida I'm really not planning on getting into extreame offroading but I want to have enough height to keep out the flood waters! Thanks for all the help and hope to stay in touch with all the locals for future wheeling!
 

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The first series of 2007 production on the Sahara came with D44 rear and 4.10 gear... I believe that 08+ is being made with D35... Being in Florida I'm really not planning on getting into extreame offroading but I want to have enough height to keep out the flood waters! Thanks for all the help and hope to stay in touch with all the locals for future wheeling!
If thats the case keep the 35's and get a snorkle... Cheaper and safer than just getting 37's
 

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Discussion Starter · #17 · (Edited)
Thanks was thinking of getting the new River Raider snorkel too! (Thats next project) There are several memebers of our club (SFJC) that have JK Rubicons running on 37's and look absolutely awesome! For now, I'll probably stick with the 35 and minimize any risk to the Sahara... Thanks for the help!
 

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Yeah...I think your axles are going to be fine. What I plan to do before going up to 37s is new driveshafts and regear (I am currently at 4.10 but want to go up to 5.13), throw on some stonger U joints....damn, now I'm just going into "wish-list" mode.
 

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My bad I just noticed you had an 07 d30??????? not sure on that one some one else will have to chime in
Does that mean the 08 SAHARA have D44 up front?
 
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