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Hi Everyone, i have a 2014 JKU Sport with a 3.5” AEV Dual sport lift, rear ARB Locker, upgraded rear spline, G2 upgraded rear axel shaft, 4.56 gears. Front is still a Dana 30 with welded gussets. I’m currently running 35” BFG All terrains. I would like to go a little bigger on the tires. My options are to either go with a different brand tires, since BFG’s run a little smaller or go to 37” BFG’s or Nittos. I use the Jeep but on and off road. I don’t want to upgrade to a pro rock 44. Do you think adding axel sleeves and truss to my current Dana 30 with gussets will do fine with 37’s? BFG 37’s weight about the same as nitto 35’s. Is it the weight of the tires?? Any advice would be appreciated. If I would be flirting with possible issues then i will stick to what I have had for the past 4 years...... just wanted to change it up a bit.
 

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My 37's are great and way better than 34" and 35's in my opinion, that said it opened things up to building my JKUR for them. I have done a BBK to the fronts, 4.88 gearing, 1 Ton steering with HD tie rod and draglink, teraflex ball joints and welded gussets on the C's so far. Up next are chromoly axles front and rear, brake upgrade on the rear, PSC big bore box and Adams driveshafts to finish it out. I take it easy when off roading and I run a difficult trails now and then so I will see how my front D 44 holds up to it. If it does not I will pick up a Pro rock for the rig. Your D 30 should be ok with trussing it ect. Just go easy with the skinny pedal and when on tough sections of a trail. Your center section will be the weak point in the front diff.
 

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It is more than just weight. I personally would not run 37s on a D30 front. 4.56 is undergeared for 37s as well.
 

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I love my 37's. But it comes with a price if you want to do it right.


Sent from my moto g(6) using Tapatalk
 

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While you may get away with running BFG 37's (which are really about 35.5") on a D30, personally I would not because you aren't geared for tires that big. I would want at least 4.88 gears to run those tires. In fact, I have 4.88 gears and run those tires. Sometimes I wish I had 5.13 gears. I never wish I had 4.56 gears. I upgraded to a D44 up front, not sure how big a difference that makes. Also upgraded ball joints, now axle shafts, brakes, and in the future a tie rod.
You can do what you want, but if you want to run bigger tires you should be prepared to spend the money required to run bigger tires. If you aren't willing to spend the money to do it right, either don't do it or be prepared to spend the money to fix what broke (which will likely be more money then it would have cost to do it right).
 

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I ran 37's on a dana 30 for 2 years and only broke one greasable u-joint. Only had c gussets as well. It can be done if you wheel sensibly. I had 4.88 gears and true tracs. 4.88 is even borderline for 37's in my opinion. Im currently on one tons and 5.38 and thats barely suffecient with the 3.8l engine.

I would truss the axle and get a set of rare parts ball joints if you plan on keeping the dana 30 for a while. You can run 37's on it if your easy with the skinny pedal and know when to pull line.
 
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While you may get away with running BFG 37's (which are really about 35.5") on a D30, personally I would not because you aren't geared for tires that big. I would want at least 4.88 gears to run those tires. In fact, I have 4.88 gears and run those tires. Sometimes I wish I had 5.13 gears. I never wish I had 4.56 gears. I upgraded to a D44 up front, not sure how big a difference that makes. Also upgraded ball joints, now axle shafts, brakes, and in the future a tie rod.
You can do what you want, but if you want to run bigger tires you should be prepared to spend the money required to run bigger tires. If you aren't willing to spend the money to do it right, either don't do it or be prepared to spend the money to fix what broke (which will likely be more money then it would have cost to do it right).
KM3's run 36.5" mounted and 36" with the weight of the Jeep on them, at least in the 17" D rated version. 4.56 gears are ok most of the time, 4.88's would be a better match.

As you mentioned correctly, one will need to beef up the steering, brakes, axle and I would highly recommend something like Dynatrac ball joints as you will be replacing ball joints frequently. Any ball joint that's not rebuildable on the vehicle just doesn't make sense unless you really like replacing ball joints.
 

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KM3's run 36.5" mounted and 36" with the weight of the Jeep on them, at least in the 17" D rated version. 4.56 gears are ok most of the time, 4.88's would be a better match.
I concur that my KM3 37x12.50R17D are 36.0" at 28 PSI calibrated with GPS. I am geared at 5.13 with a MT and I could not see going any lower in gearing.
 

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I concur that my KM3 37x12.50R17D are 36.0" at 28 PSI calibrated with GPS. I am geared at 5.13 with a MT and I could not see going any lower in gearing.
I agree with 5.13 for 37's even though a lot of people run 4.88 and claim is fine.

This is my logic; all manuals factory JK Rubicons came with 4.10 and 32's so I think is safe to say that 4.88 should be ideal for 35's and 5.13 for 37's.
 
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35 vs 37 tires

I have a 2013 Rubicon Unlimited 6 speed manual with 4.10 gearing. I upgraded to 35's then later to 37" tires and loved the look... especially of the 37's! With the 4:1 transfer case it was OK on the trails even with the 37's unless heavy rock climbing was involved. However, I also do a LOT of highway driving and the extra drag of the aggressive 37's made a huge difference in my MPG on the highway. I cut back to 35's as a compromise but still change to "commuter" tires for long hauls when I have to travel to other states.


If I were to do trails only(or mainly) I would definitely have kept the 37's. Prior to putting my original 35's on I beefed up the front D44 including upper and lower "C"'s.


My $.02 worth


KG6SLC aka Eugene
 

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37s are awesome if you wheel. But if you wheel, you’ll want to do it right. Realistically, that means probably $8-10k for a regear, an upgraded front axle (eg ProRock 44), chromoly axle shafts, upgraded ball joints, big brake kit, new drive shafts, Hydraulic assist steering kit, and new wheels (eg beadlocks), among other things. My advice is to be realistic about your budget and intended use. If hardcore wheeling is not in your plan, stick with 35s and save a bucket of dough.
 

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37s are awesome if you wheel. But if you wheel, you’ll want to do it right. Realistically, that means probably $8-10k for a regear, an upgraded front axle (eg ProRock 44), chromoly axle shafts, upgraded ball joints, big brake kit, new drive shafts, Hydraulic assist steering kit, and new wheels (eg beadlocks), among other things. My advice is to be realistic about your budget and intended use. If hardcore wheeling is not in your plan, stick with 35s and save a bucket of dough.

This is great information. For me going from 2.5” lift and 35’s to 37’s “the right way” put me back over 15k though.. I have an excel spreadsheet I can post later with the exact details. I use it to keep track of everything I’ve done and put the brakes on spending more money on things like larger axles. I still need to buy beadlocks.. It’s getting old and expensive re balancing my tires after every major run. I have no regrets and glad I took the leap. #Goals
 

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37s are awesome if you wheel. But if you wheel, you’ll want to do it right. Realistically, that means probably $8-10k for a regear, an upgraded front axle (eg ProRock 44), chromoly axle shafts, upgraded ball joints, big brake kit, new drive shafts, Hydraulic assist steering kit, and new wheels (eg beadlocks), among other things. My advice is to be realistic about your budget and intended use. If hardcore wheeling is not in your plan, stick with 35s and save a bucket of dough.

This is great information. For me going from 2.5” lift and 35’s to 37’s “the right way” put me back over 15k though.. I have an excel spreadsheet I can post later with the exact details. I use it to keep track of everything I’ve done and put the brakes on spending more money on things like larger axles. I still need to buy beadlocks.. It’s getting old and expensive re balancing my tires after every major run. I have no regrets and glad I took the leap. #Goals
Lol. Yeah, $15k is probably more like it. I was subconsciously trying to make myself feel better about the expense. 😂
 

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I think I got out of it for less than $15K but....

I already had new driveshafts and the front big brake kit with enhanced rear pads.

So, it was right at $5K for the Core 44 axle, ARB and RCV's. I got a set of Clayton adjustable control arms, it cost me $400 for the arms and about $75 to rebuild the bushings that needed some attention and a rattle can of paint. $800 for upgraded tie rod and drag link, $450 for a lightly used PSC big bore steering box, $200 for unit bearings, $555 for Dynatrac ball joints (now these are replacements for the original G2's but on 37's, you really should go this route first) $350 for steel wheels, $350 for DIY beadlock rings, $40 for a spool of welding wire and sanding wheels. $40 for new tires (yes, I won them in a raffle so that significantly cut my costs. $100 for spring spacers. $500 for rear chromolly axle shafts.

So, my actual output to actually make the move to 37's was just under $8500. However if you factor in the real cost of the tires, add another $2K. Now the previous work I did was close to another $1500 (brakes, drive shafts). If I bought everything new, yes, I could have easily hit $15K.
 
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