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Discussion Starter · #1 ·
Figured I would ask the community for their opinion...

In a few months, I plan to install LSD and a locker in my 2012 Sahara, and figured while I am in there, I might as well re-gear. I have 3.21s, and 33x12.5x15 Duratracs. I'm not wanting for power, but 5th on 55mph roads has become useless, as it lugs too much (can't get the eco light to even turn on unless on completely flat surface) so I figured I'd throw in 4.10s in case I want to upgrade to 35s later down the road. My concern however is simple...I remember reading that 4.10s have more teeth than 3.21s, thus, weakening the entire assembly. Is that true? I don't rock crawl but am planning on a few trips to Colorado and Utah (again, no serious crawling) and don't want to compromise the strength of the D30 up front. I don't do enough serious wheeling (live in NJ) to warrant a D44 upgrade. I also wanted to re-gear since adding a winch, a rear bumper, a roof rack, and an air compressor will add close to 500lbs of extra dead weight.

Any thoughts? Are there 4.10s that are stronger than others?
 

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The biggest problem with short gear sets is that the pinion gets smaller as the number gets bigger. The makers of the gear sets do their best to give you as much strength as possible by changing the numbers and sizes of teeth on the ring and pinion. Dropping a tooth on a smaller pinion means the remaining teeth can be strong enough to handle the load.

The biggest issue with the D30 is not the gears. It's the case. It's light weight and tends to flex under load when you have short gears and heavy tires. Even more so when you put a lot of torque through it (by means of upgraded engine or deep gears in the trans or t-case). When the case flexes, the gears don't mesh properly and start to break. Not because the gears are weak but because they're not designed to flex around like they do.

If you keep the engine, trans and t-case pretty much stock and you're not going to seriously crawl with it, 4.10's and 35" tires aren't going to be a problem at all.

Still, if you're really worried about it, there are a few things you can do to reduce case flex. For some reason I'm blanking on what it's called but I've seen people put a specifically machined steel piece that bolts on top of the bearing caps and ties the case together for a little added strength. That along with a heavy duty diff cover (there are several out there) will reduce your case flex.
 

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Discussion Starter · #4 ·
Excellent info. So running 4.10s, an Eaton locker and one of those diff covers and 35" tires in a D30 without climbing boulders and heavy flexing should be pretty stout right? If you are familiar with the colorado/moab trail books, I am looking to do the easy/moderate where the author states a 4x4 with big tires and a minor lift can get by, not the stuff you see in the moab competitions.
 

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The diff girdle will help strengthen the diff itself, but have you also considered sleeves for the axle tubes and gussets for the "Cs" to strengthen the rest of the housing?
 

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Perhaps derf is referring to a differential girdle.
LPW Support Cover, Differential Cover, Rear End Girdle
I think girdle is the right term but that doesn't look like what I'm talking about. That looks like it's just a heavy duty cover.

What I'm thinking of goes inside the diff. It starts as a plate of steel that gets machined so that it has 4 bolt holes that line up with the bolts that hold the bearing caps on and a big hole in the middle to go around the carrier and gears. You bolt it on and it ties the bearing caps together to reinforce them and keep them from flexing.

Engine builders do the same thing with the main caps to stiffen up the bottom end of an engine block by running the main cap bolts through it. It's an engine main girdle and looks like this: ls1/ls6 engine main girdle,increases strength of the main caps

Once you have that on, you can bolt on a heavy duty cover that reinforces the entire outer case for added strength on top of that.



But also, I agree with sleeving the axle tubes and gusseting the outer ears while you've got the axle apart to do the gears. That addresses the other half of the weakness of the D30 when it comes to larger tires.
 

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Excellent info. So running 4.10s, an Eaton locker and one of those diff covers and 35" tires in a D30 without climbing boulders and heavy flexing should be pretty stout right? If you are familiar with the colorado/moab trail books, I am looking to do the easy/moderate where the author states a 4x4 with big tires and a minor lift can get by, not the stuff you see in the moab competitions.
I was just there this summer and took an entirely stock JK rental over what the book called "easy" trails (Engineer pass and Imogene pass in Ouray) without having any trouble at all. 35's would be overkill for trails like that.

FWIW, my avatar picture is me at the top of Imogene pass.
 

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Discussion Starter · #8 ·
The diff girdle will help strengthen the diff itself, but have you also considered sleeves for the axle tubes and gussets for the "Cs" to strengthen the rest of the housing?
No. Don't want to do that. It is far too much stuff what I am planning. I am installing the locker just in case and the 4.10s for a little extra pep. I am not planning on wheeling anywhere a STOCK Sahara couldn't go.
 

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Discussion Starter · #9 ·
^Edit...what's the cost of something like this? I have read countless threads that if you are doing what I am doing (trying to beef up the D30) to this extent, you might as well swap in the D44.
 

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Just curious...
Have you done the match on a trade-in for a Rubi since you are going to 4.10's and a locker (up front)?
 

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^Edit...what's the cost of something like this? I have read countless threads that if you are doing what I am doing (trying to beef up the D30) to this extent, you might as well swap in the D44.
The axle tubes and the inner "c"s on the D30 and the D44 are about the same; so even upgrading to the 44, you should still sleeve and gusset when you run over size tires. Or install an axle truss to do the same thing.
 

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Discussion Starter · #12 ·
Just curious...
Have you done the match on a trade-in for a Rubi since you are going to 4.10's and a locker (up front)?
I already have tons invested in the Sahara, and the Rubicon won't give me anything I want really for the money. I will take a bath on the Rubicon trading in my Sahara. I will lose at least 5K.
 

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I already have tons invested in the Sahara, and the Rubicon won't give me anything I want really for the money. I will take a bath on the Rubicon trading in my Sahara. I will lose at least 5K.
Do you want the LSD and lockers for weather (snow & rain)? Dumb question- I only ask because it doesn't seem like the types/frequency of off-roading you plan to do requires a locker.
But with you on the trade. Already modded my wee 3.21 too much to trade her in now....4.10s or 4.56s eventually.
 

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Discussion Starter · #14 ·
Do you want the LSD and lockers for weather (snow & rain)? Dumb question- I only ask because it doesn't seem like the types/frequency of off-roading you plan to do requires a locker.
But with you on the trade. Already modded my wee 3.21 too much to trade her in now....4.10s or 4.56s eventually.
I want a locker up front for those VERY VERY rare just in case situations, and a true LSD in the rear for daily driving. I am planning on keeping my Sahara for a long long time (if not forever) so I don't mind turning it into a rubicon. I don't need the electronic discos, and the wheeling I do the D30 is plenty strong enough. I just want to make it capable for anything I am going to throw at it.
 

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:thumb:
Understood. Building my own Sporticon so I could put in what I wanted. Got a great deal on my Sport- but thanks to the forum I'll probably wind up spending just as much as a Rubicon. :surrender: :D
(WARNING: too many smileys in this post).
 
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