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Hi all,

I purchased my first jeep a few months back and have been enjoying both working on it and driving it a ton! I made a big mistake of not doing my part studying about what was all needed in a 4x4 vehicle, etc when I bought it. I think i just got more excited than anything. Well onto my point I purchased a nice well kept 2012 jku that was pre lifted (3.5in) and the owner already had 37s on there. I didn't know anything about gears, lockers, etc then, and now after a lot learning I realized that I am very lucky nothing has broke yet.

The jeep is still geared on 3.21(no wonder it's sluggish), with of course Dana 30/44's. I am planning on this next week welding on some Gussets, as well as install a axle sleeve on the 30. I have already started getting quotes for a regear and was planning on either 4.56 or 4.88. Cost estimates about $1900-2200 for gears/seals/bearings which feels like about average going from 3.21 here in Utah.

However, I am unsure if I should throw some lockers on for at least the rear, or maybe both. I still am on a college budget so my options are limited. I was thinking maybe a Eaton Detroit Trutrac at least in the rear, or even both if it would be worth it in the 30s. I really only do mild trail, and just use it around town, but would like to feel confident in tackling some mild crawling. So in conclusion:
1. Best regear for 37s?
2. Which lockers would fit my re gear, would it be worth saving for better lockers in the future or throwing some in while re gearing?

Is there anything else I am missing? I just want to make sure I do it right, and feel at ease on the trail.

Thanks!
 

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Sell the 37s and switch to 35s.

Go with 4.56 if mileage is important, 4.88 if perceived power is important.

Skip the lockers. Based on the description of what you intend to do, they’re not necessary.

If notwithstanding the above you decide to go with lockers, just do the rear. Locker on a Dana 30 is a bad idea, although I’m sure others will comment about how they did it for years without issue.
 

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If you are going to wheel it, especially wheel it around Moab, you may want to either upgrade the D30 in front or downgrade to 35" tires as fiend suggested. "mild trails" can be relative.
For 37's the most popular ratio is probably 5.13, and that is probably farther than most want to go on a D30. I am not sure it is worth spending money on the D30 trying to make it stronger. Because nothing you can do to it will address the biggest weakness of a D30 (the small ring and pinion). Everything else about it is about the same as a D44. If you don't need beyond 4.56 gears you would likely be fine with the D30. But start going further and the size of the gears can become an issue. With 35" tires 4.56 gears should be fine. You may even get away happily with 4.88 gears. But most don't go past there. And 4.88 gears I would consider the minimum for 37's. And as someone who has 4.88 gears and 37's I can tell you it is not ideal. I wish I had 5.13 gears.
I'm not sure I would lock a D30, I would rather use a TrueTrac mechanical LSD if you want to put something in the D30. And based on your indicated usage, I think TrueTracs would be better anyway, whether just the rear or front and rear.
 

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Discussion Starter #4
If you are going to wheel it, especially wheel it around Moab, you may want to either upgrade the D30 in front or downgrade to 35" tires as fiend suggested. "mild trails" can be relative.
For 37's the most popular ratio is probably 5.13, and that is probably farther than most want to go on a D30. I am not sure it is worth spending money on the D30 trying to make it stronger. Because nothing you can do to it will address the biggest weakness of a D30 (the small ring and pinion). Everything else about it is about the same as a D44. If you don't need beyond 4.56 gears you would likely be fine with the D30. But start going further and the size of the gears can become an issue. With 35" tires 4.56 gears should be fine. You may even get away happily with 4.88 gears. But most don't go past there. And 4.88 gears I would consider the minimum for 37's. And as someone who has 4.88 gears and 37's I can tell you it is not ideal. I wish I had 5.13 gears.
I'm not sure I would lock a D30, I would rather use a TrueTrac mechanical LSD if you want to put something in the D30. And based on your indicated usage, I think TrueTracs would be better anyway, whether just the rear or front and rear.

Okay so after a lot of thought I think my plan is to be safe and just eat the initial cost, I am going to go Prorock 44 and replace the 30 upfront, then regear to 4.88 or 5.13(most likely 5.13)as long as its safe for the rear dana 44. And then have the shop just truss/gussett/sleeve the back with the eaton detroit trutrac. I think with that I really just need to worry about changing my brakes on the 30, the rest comes with the prorock. I feel doing it right now will save me lots of headache and time later. Last thing I want is to be stuck on a road 100 miles in on my broken dana 30. anything else im missing?

Thanks, I really appreciate the advise!
 

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Okay so after a lot of thought I think my plan is to be safe and just eat the initial cost, I am going to go Prorock 44 and replace the 30 upfront, then regear to 4.88 or 5.13(most likely 5.13)as long as its safe for the rear dana 44. And then have the shop just truss/gussett/sleeve the back with the eaton detroit trutrac. I think with that I really just need to worry about changing my brakes on the 30, the rest comes with the prorock. I feel doing it right now will save me lots of headache and time later. Last thing I want is to be stuck on a road 100 miles in on my broken dana 30. anything else im missing?

Thanks, I really appreciate the advise!
Well, that is a start.
As mentioned plenty of times on here, the difference in cost to properly run 37's vs running 35's is pretty big. You may find you also have steering issues, those big tires can be hard to turn, especially when you are in the rocks. Also, the stock tie rod isn't very stout, and with big tires you may want to upgrade it. I suggest an aluminum tie rod. You may also want a drag link flip with that much lift. Speaking of which, what 3.5" lift does it have? What does it have for caster correction? Did they do anything to address the steering geometry? Are the ball joints stock? Or have they been upgraded (37's really could use stronger ball joints)?
Welcome to the deep end of the pool.
 

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To the OP: not to be a downer, but running 37s the right way, especially to be capable of wheeling in rocky terrain with good reliability, is an $8-10k proposition. Upgraded housing, ball joints, big brakes, new drive shafts, hydro steering, the list goes on. Not trying to dissuade you, just know what you’re getting into. Your original post said you’re on a student budget and would be doing mild rock crawling at most. Those assertions seem incongruous with building up a rig on 37s and incurring the necessary expenses. But if you have the funds and are interested in getting more deeply into wheeling, the opportunity presents.
 
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