37's on D30's?
JK-Forum Founder
Joined: Jul 2006
Posts: 36,534
Likes: 16
From: Laguna Niguel, CA
You do need to remember that Eddie got a ton of miles out of his D44 with chromoly shafts and big tires.
And, when his chromoly shaft exploded and took other parts with it, he was doing some heavy rocks with a higher than crawl speed spin and sudden traction.
His is probably a heavier than most JKs, and he was running one of the heaviest 37" tires available--putting more strain on components.
Metal fatigues over time with use. I'd say that he definitely got his money's worth for his front setup--especially considering that his stock rear locker could not survive his preferred wheeling habits/locations. (He has been running a rear Sahara Dana 44 with an ARB locker and chromoly shafts for some time.)
If you don't lock a Dana 30, if you baby it and don't put it in spin-with-sudden-traction situations, and if you run a lighter tire/wheel combination, you could put quite a few miles on 37s before it fails. As long as you know that it is a temporary thing, it could meet your expectations.
However, if you wheel locked in the rocks, deep mud or snow, with a heavy rig, with a heavy wheel/tire combination, even a trussed/sleeved/gusseted Dana 44 with Chromoly axle shafts will eventually fail with 37s. It isn't bombproof.
I wheel some challenging stuff, but it will probably take me 10 years to put as many hard miles on my JK as Eddie did in about 3 years. If I can get 10 years out of my Dana 44 with 37s, sleeved and gusseted with chromoly shafts, I would be very happy.
The way I wheel, I wouldn't go higher than 35s with a sleeved/gusseted/chromoly shaft/ARB built JK Dana 30.
And, when his chromoly shaft exploded and took other parts with it, he was doing some heavy rocks with a higher than crawl speed spin and sudden traction.
His is probably a heavier than most JKs, and he was running one of the heaviest 37" tires available--putting more strain on components.
Metal fatigues over time with use. I'd say that he definitely got his money's worth for his front setup--especially considering that his stock rear locker could not survive his preferred wheeling habits/locations. (He has been running a rear Sahara Dana 44 with an ARB locker and chromoly shafts for some time.)
If you don't lock a Dana 30, if you baby it and don't put it in spin-with-sudden-traction situations, and if you run a lighter tire/wheel combination, you could put quite a few miles on 37s before it fails. As long as you know that it is a temporary thing, it could meet your expectations.
However, if you wheel locked in the rocks, deep mud or snow, with a heavy rig, with a heavy wheel/tire combination, even a trussed/sleeved/gusseted Dana 44 with Chromoly axle shafts will eventually fail with 37s. It isn't bombproof.
I wheel some challenging stuff, but it will probably take me 10 years to put as many hard miles on my JK as Eddie did in about 3 years. If I can get 10 years out of my Dana 44 with 37s, sleeved and gusseted with chromoly shafts, I would be very happy.
The way I wheel, I wouldn't go higher than 35s with a sleeved/gusseted/chromoly shaft/ARB built JK Dana 30.
as far as the sahara 44 that i WAS running goes, i blew out my brand new 5.38 ring gear in just over a month and after about 10 runs. granted, i was pushing 40's at the time. right now, moby dick has been sitting in the garage for over a month out of commision.
JK-Forum Founder
Joined: Jul 2006
Posts: 36,534
Likes: 16
From: Laguna Niguel, CA
There's a big gaping hole in this... The ENTIRE front end of the vehicle suffers. Forget the guts of the axle. They're easy and obvious -- Superiors and CTMs and you've got tough axles. The carrier and gears are still tiny and get pummelled when things let go. And they also get pummelled when things DON'T let go when they should.
The housings can be gussetted to be better, but you still have a TINY ball joint that is taking a wicked beating. D44 or D30. You have a small unitized bearing that's nonserviceable. Get em wet and they die fast.
And then there's the steering. Without hydro assist, you can't steer big tires in big rocks. Assist is hard on ball joints and tie rod ends. Without the assist, all that pressure is on the drag link and steering box. The little steering box isn't capable of holding 37s in a bind without showing some damage in a big hurry.
Front track bar? Rip off the frame if you get unlucky.
Getting the sense that this may not be as easy as you had hoped? Depends a lot on your intended usage. If you want to go run the bunny trails, a LOT of this doesn't apply. If you want to get off the porch and run with the big dogs, you need to be addressing your car like a system, not individual components.
The housings can be gussetted to be better, but you still have a TINY ball joint that is taking a wicked beating. D44 or D30. You have a small unitized bearing that's nonserviceable. Get em wet and they die fast.
And then there's the steering. Without hydro assist, you can't steer big tires in big rocks. Assist is hard on ball joints and tie rod ends. Without the assist, all that pressure is on the drag link and steering box. The little steering box isn't capable of holding 37s in a bind without showing some damage in a big hurry.
Front track bar? Rip off the frame if you get unlucky.
Getting the sense that this may not be as easy as you had hoped? Depends a lot on your intended usage. If you want to go run the bunny trails, a LOT of this doesn't apply. If you want to get off the porch and run with the big dogs, you need to be addressing your car like a system, not individual components.
in addition to breaking a chromo shaft and locker, i've gone through 2 steering boxes and tore off my track bar mount at the frame before upgrading to a prorock 60.
Sorry to hijack, but this seems relevant to this discussion.
Does this go to prove that gears also become problematic (read: weak teeth) at some point?
I am currently considering gears for my D44 and 35" tires... I am considering 4.88s in this weak powered JK. A lot of people on the fourm seem to be pushing 5.13s and/or 5.38s.... do these also become a weak point (Again, read: weak/small gear teeth) in either a D30 or D44?
Does this go to prove that gears also become problematic (read: weak teeth) at some point?
I am currently considering gears for my D44 and 35" tires... I am considering 4.88s in this weak powered JK. A lot of people on the fourm seem to be pushing 5.13s and/or 5.38s.... do these also become a weak point (Again, read: weak/small gear teeth) in either a D30 or D44?
Last edited by wayoflife; Oct 18, 2009 at 08:56 AM.
JK Enthusiast
Joined: Mar 2008
Posts: 184
Likes: 1
From: VA
Not even remotely surprised. Add Johnson Valley to your list and it gets uglier.
God I miss it!!!
JK Enthusiast
Joined: May 2009
Posts: 303
Likes: 1
From: Dubai
Good thread and all good points, im fairly new to JK's and just learning about them really. i've just installed 33's on a sahara and although 33's are a long way short of 37's, I can see that the extra weight and forces involved could easily shred components.
I keep wondering whether im going to break something with 33's 3.21 gears and a dana 30 front axle? (slightly off topic, sorry)
Cant begin to imagine what its like trying to make sure 37's dont break stuff.
I keep wondering whether im going to break something with 33's 3.21 gears and a dana 30 front axle? (slightly off topic, sorry)
Cant begin to imagine what its like trying to make sure 37's dont break stuff.
Thread Starter
JK Super Freak
Joined: Aug 2009
Posts: 1,314
Likes: 1
From: Stamford, CT
Great comments by all. Really appreciate everyone's input and knowledge from first hand experience. I'm not ready to tackle any 5+ rated trails anytime soon. So I'm not planning on wheeling that hard until the Jeep is setup right. I'm at the beginning and trying to plan my mods as economical as possible. I do eventually want to end up with 37's with the jeep built up to truly wheel them but we all know it's an expensive venture. I do want to eventually get a stronger front axle down the road as well as other components, but the D30 will have to do for now. 35's don't seem THAT far away from 37's, their still a heavy tire so breakage is very possible with those as well. I just figure getting 37's now will get me a little closer to the look I want and build around that. 
JK Enthusiast
Joined: Mar 2008
Posts: 184
Likes: 1
From: VA
Each step is a step. Though a 37 isn't THAT much bigger than a 35, its substantially bigger than the 32 that the factory equips the car with.
Good to plan long term, even if you can't own that vehicle straight away. I've spent an OBSCENE amount of money from building stepwise. But I learned something about each vehicle every step of the way... so there is an advantage both ways.
Good to plan long term, even if you can't own that vehicle straight away. I've spent an OBSCENE amount of money from building stepwise. But I learned something about each vehicle every step of the way... so there is an advantage both ways.
JK Super Freak
Joined: Nov 2008
Posts: 1,090
Likes: 0
From: East Coast
It really depends on how you wheel. I know with the trails I've run, my d30 has held up fine. I would certainly not be out on rocks testing the limits just yet. I have the stock X axles, fully open d30 front and d44 rear. I haven't really had any issues and I am running 35s. I even have stock driveshafts with my 4" lift. I know the ds will become an issue sooner rather than later, but the few times I have actually disconnected and bottomed out on the bumpstops, I have still been ok. I would say to successfully run 37s, you would have to beef up the d30 quite a bit. Even once properly reinforced, I would not be doing crazy throttling, hitting rocks where theres sudden traction, etc. Definitely wouldn't be doing some of the higher horsepower/heavier throttle pedal stuff. That being said, 35s on a d30 are extremely capable.
My plans are essentially this:
Off Road Evo Gussets
Off Road Evo Sleeves for Front D30
Front Axle Super 30 upgrade w/ ARB air locker
Rear Axle upgrade w/ ARB air locker
ARB Air Locker Tank w/ Tire Inflation
ARB Pump and Lines for Inflation
Rubicon Express Stainless Steel Airlines for ARB Locker, Front and Rear
Yukon JK 4.88 Front and Rear with Overhaul Kit
Front and Rear J.E. Reel 1350 driveshafts
Crown extended brake lines, Front and Rear
ARB diff covers, Front and Rear
I know Rock Krawler even sells a weld-on truss for the long side of the axle tube on the d30. Way I see it, everything I have outlined above should come in around $4000, which upgrades both axles extensively for the cost of a d60. While it won't be as strong as having a d60 up front, I think you will find the list will build a more than capable rig. I plan on continuing to run 35s, but I am sure I could run 37s on this new setup no problem.
My plans are essentially this:
Off Road Evo Gussets
Off Road Evo Sleeves for Front D30
Front Axle Super 30 upgrade w/ ARB air locker
Rear Axle upgrade w/ ARB air locker
ARB Air Locker Tank w/ Tire Inflation
ARB Pump and Lines for Inflation
Rubicon Express Stainless Steel Airlines for ARB Locker, Front and Rear
Yukon JK 4.88 Front and Rear with Overhaul Kit
Front and Rear J.E. Reel 1350 driveshafts
Crown extended brake lines, Front and Rear
ARB diff covers, Front and Rear
I know Rock Krawler even sells a weld-on truss for the long side of the axle tube on the d30. Way I see it, everything I have outlined above should come in around $4000, which upgrades both axles extensively for the cost of a d60. While it won't be as strong as having a d60 up front, I think you will find the list will build a more than capable rig. I plan on continuing to run 35s, but I am sure I could run 37s on this new setup no problem.
Thread Starter
JK Super Freak
Joined: Aug 2009
Posts: 1,314
Likes: 1
From: Stamford, CT
Joneszj, your list is very close to the path I want to go. I wondered with chromo axles 30 spline if that would make it as strong as the stock d44 axle. If so I would go that route. However I also realize the R&P would not be as strong due to smaller diameter size compared to d44. I also agree it's how you wheel and I tend to avoid any full throttle scenarios on the rocks. Mud maybe yes.
JK Enthusiast
Joined: Jan 2007
Posts: 181
Likes: 0
From: Reno, NV
If you hammer down in the mud you are asking for it with a D30 and 37s... Just sayin. Take the advice of many and grab a D44 or higher. Is there that big of a price gap between buying a Rubi take off and pimping out a D30?? Total guess, but 1k for axles/u-joints, 1k for an ARB, and 500 for the housing or so am I right? What do bent out of whack Rubi 44s go for these days? As long as you find one with the steering intact, just get the thing retubed (make sure to shop around as labor for this definitely varies).
~Casey
~Casey
Thread Starter
JK Super Freak
Joined: Aug 2009
Posts: 1,314
Likes: 1
From: Stamford, CT
If you hammer down in the mud you are asking for it with a D30 and 37s... Just sayin. Take the advice of many and grab a D44 or higher. Is there that big of a price gap between buying a Rubi take off and pimping out a D30?? Total guess, but 1k for axles/u-joints, 1k for an ARB, and 500 for the housing or so am I right? What do bent out of whack Rubi 44s go for these days? As long as you find one with the steering intact, just get the thing retubed (make sure to shop around as labor for this definitely varies).
~Casey
~Casey
Also, with taking in all the comments, It looks like I'll go with 35's after all said and done.