High travel, high clearance & high octane, a streetable adventure LJ story

toximus

TJ Addict
Mar 29, 2018
1,414
Northern WI
This new build thread comes at the intersection of my previous "Red the LJ" build thread and a honest conversation with Blaine (MrBlaine here on the forums) where, put simply, he told me that I need to start all over.

After a day of mulling it over, start over I did.
 
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toximus

toximus

TJ Addict
Mar 29, 2018
1,414
Northern WI
Up until now I've treated my build like a Lego project. Building a little here and there, and when something broke I upgraded it. Not that there's anything innately wrong with that building style but I wanted more and the building bug has bitten me HARD. After talking with Blaine I started to have a deeper understanding of the complications that one component can have on another. I couldn't just slowly build what I had into what I wanted I had to jump ship and swim into the uncomfortable.

I listed parts for sale from my previous build that I wouldn't need and continued to refine the details and specs of my build.

Blaine had me pick a few specs to build to:
  • Tire size that I won't change from.
  • Belly height.
  • Wheelbase.
All of these effect each other. Change one and you must change another.

I decided on a balance for travel and clearance.
 
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toximus

toximus

TJ Addict
Mar 29, 2018
1,414
Northern WI
In order to accomplish my chosen specs I decided on fitting 2.5x14" coilovers on all 4 corners, mid-arm 4/3-link, and 37" tires. The stock 105" LJ wheelbase is ideal for the 37s and they'll allow for higher up travel compared to 40s. By running 37s on an LJ the overall offroad ability should be similar to a TJ on 35s.

Some challenges I'll face are that I want to keep my Jeep as narrow as possible to better fit on some of the narrow forest trails we have in Northern WI and Upper MI. I'll be using wider 65" WMS axles to get a little more stability but will still need to narrow the frame and tub in the back to fit in the 2.5" coilovers. Another challenge is that I want to keep my Jeep sealed to keep rain, snow, and dirt out. That's going to require some body work. I have also never welded before so this is going to be fun!

---

The axles arrived early this week on the warmest sloppiest day of the year. I had planned on meeting the semi truck with a rental truck that has a lift gate and driving it down to my garage and using a strap around the lift gate to lift the axles off the pallets but even the best laid plans sometimes don't work out. I ended up with a stuck Penske rental truck, friends stuck pickup truck, and my neighbor heard the commotion on our access road and came over with his old International tractor from his farming days and saved the day! It was a huge mess but I'm thankful for good friends and that it wasn't worse and the axles are safely in the garage!

20180327_rockjock-axles-arrived-tractor.jpg
 
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toximus

toximus

TJ Addict
Mar 29, 2018
1,414
Northern WI
The stock Dana 30/44 combo that comes on an LJ won't hold up to 37s. The biggest issue is that the stock Dana 30 outer balljoints on the front are too weak. There's enough examples of even heavily built Dana JK 44s will wear out the internals over time if ran offroad. So for axles I decided on Dana 60s. Currie makes their version, the RockJock 60, which main advantage is that the ground clearance is higher than your junkyard 60s. Along with some other improvements Currie added which are great for offroading, which I'll go over, they were also able to build to my specs which saves me a lot of time vs piecing together my own from a junkyard.

20180329_currie-rockjock-60-garage.jpg


A lot of planning went into speccing the axles to be just right for my build. It took about 2 months to get everything right on paper before giving Currie the go ahead. (As a side note, if anyone is wanting to repeat my order, make sure you buy through a reputable reseller as some of the discount resellers may not be worth the savings you receive. I purchased through Ricky at 4LowParts and he has been very helpful and had no issue putting together my order. He answered all of my questions without making me feel like I was wasting his time.)

Starting at the differentials, the RJ60VXR are a high pinion design, which results in the pinion running on the weak side of the ring gear teeth in the rear, this can cause the ring gear to deflect under high load and skip teeth. I upgraded to the RJ60VXR diff housing for the front and rear. The VXR housing adds a few benefits but the main reason I went with it was for the load bolt to prevent ring gear deflection in the rear. I also went with Ford Super 60 gears which are larger diameter and thicker than the standard Dana 60 gears. I wanted to go with a lower gear ratio in the diffs like a 6.17 but the lowest Currie will go in their housings is a 5.38, so that's what I went with, we'll have to make up for it with the engine later. ARB lockers front and rear were chosen for their reliability and ability to provide expected behavior on snowy and icy roads.

The load bolt can be seen near the middle:
20180329_rj60-pinion.jpg


For the yoke, it is high pinion (HP) which will improve driveline angles and keep the yoke out of the rocks. I went with a 1310 yoke to allow for the maximum driveline angle when at full droop, to act as a fuse to prevent damage to the transfer case, and because it's simply strong enough to run even larger tires than I will be. There's simply no reason to go to a bigger ujoint.

The rear has a AR500 steel skid under the diff, the same material that bulldozer buckets are made from. It's strong and doesn't gouge and "grab" onto rocks like an aluminum skid would. For the front Currie forgot to include a skid but for now I won't be running one up there, Blaine mentioned that the fronts like to get caught on rocks and rip off anyway( which immediately made sense when I actually thought about it). Currie is sending a skid over if I later decide to put it on.

Because of the angle of the RockJock 60 covers they built in a dip stick to check fluid levels:
20180330_rj60-dipstick.jpg


The VXR includes 3.5" .375" wall axle tubes. I omitted all of the brackets except for TJ lower control arm brackets and bridges. This will be correct for the 4 link rear and 3 link front. There is no room for coil buckets on the front at 65" WMS, even the driver's side LCA mount is partially frenched into the diff housing. Part of the reason why I'll need to go with coilovers.

20180329_rj60-lca.jpg


RCV shafts were chosen for the front for their ability to give constant wheel speed in case I need to drive home across the country in front wheel drive after breaking something in the rear. I also have a theory that they may provide better handling on snowy roads while in 4wd since they won't break traction with every revolution. RCVs added strength and warranty is a cherry on top but not a reason for upgrading.

20180329_rj60-knuckle.jpg


On the ends up front I went with a '04 Ford style balljoint design on the iron knuckles, the unit bearings are based on the F450 design and include a sane 5x5.5" bolt pattern with 1/2" studs. Front brakes will be later built by Black Magic Brakes. Yukon manual locking hubs will be used up front which are narrower and stronger than those from Warn.

The upper steering arms should have included a hole to be in shear with the lower steering arms but due to a recent change at Currie they are unable to provide those and a strange combo was sent to me instead. Currie is mailing me the correct blank steering arm design which I will be drilling to work with my custom crossover steering.

In the rear the simple option would have been to go with Explorer brakes flip the left to right to get the calipers to the front of the housings and call it a day. And that would have been fine and held up long term combined with the semifloat shafts. I wanted a 35 spline full float rear so I could drive home on a broken rear shaft if necessary and to further prevent deflection on the ring gear. The main contenders here were either expensive and complex designs made for Ultra4, full size truck brakes, or Currie's Wilwood brake kit. But I didn't want to compromise or run junk brakes. I ended up going with the Currie JK floater spindle (https://www.currieenterprises.com/CE-0013JK5L). This full float design uses OEM JK brakes which are reliable, available, and they'll allow to me have the correct 75/25 braking ratio with the front without messing around with a proportioning valve. Awesome! With some ingenuity I should be able to make the parking brake connect up with the TJ cables. They are finished off with Currie drive flanges. Oh, and Currie welded the snouts to opposite sides for me so that there would be more room for coilovers in the rear by placing the calipers on the front!

20180330_rj60-full-float.jpg


20180330_rj60-jk-brakes.jpg


The 3.5" tubes are sleeved down for the rear snouts and JK backing plates:
20180330_rj60-brake-flip.jpg


Pictures don't do these axles justice. They are large, beefy, and precise without being overkill.

20180329_rj60-diff-cover.jpg
 
Last edited:

JMT

The Jeep Guy
Supporting Member
Ride of the Month Winner
Feb 27, 2017
7,318
Texas Hill Country
Up until now I've treated my build like a Lego project. Building a little here and there, and when something broke I upgraded it. Not that there's anything innately wrong with that building style but I wanted more and the building bug has bitten me HARD. After talking with Blaine I started to have a deeper understanding of the complications that one component can have on another. I couldn't just slowly build what I had into what I wanted I had to jump ship and swim into the uncomfortable.

I listed parts for sale from my previous build that I wouldn't need and continued to refine the details and specs of my build.

Blaine had me pick a few specs to build to:
  • Tire size that I won't change from.
  • Belly height.
  • Wheelbase.
All of these effect each other. Change one and you must change another.

I decided on a balance for travel and clearance.
Ok, it is a tease, so explain how changing the belly height will affect the tire size you run or vice versa. I’m at a loss on that one...
 

Kiwi TJ

If people ar talking behind ur back,then just fart
Supporting Member
Ride of the Month Winner
May 3, 2016
3,771
Auckland New Zealand
wow those are some meaty axels...I did hear that there we some girders missing from the golden gate bridge, I wondered where they went haha
 
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toximus

toximus

TJ Addict
Mar 29, 2018
1,414
Northern WI
Ok, it is a tease, so explain how changing the belly height will affect the tire size you run or vice versa. I’m at a loss on that one...
Firstly, you need to ask yourself what you are building for: mall crawling, hill killing, mudding, rock crawling -- the only wrong answer is the one where you lie to yourself. If you are building for strictly hill climbing the longest wheelbase you can shove under your Jeep is probably a fairly good idea. For desert racing the most travel you can fit in is a good idea. I'm chasing ideals for crawling with a touch of Ultra4 inspiration thrown in, which is based on a proven observed ratio of what works.

A TJ is ideal for what I am building for on 35s and a 100" wheelbase, this results in a breakover angle (determined by belly height of Y) of X.

An LJ takes a bit more to be able to run the same trails as that TJ. To have the same breakover angle of X in an LJ you must run 37" tires. But now if you are running the same belly skid as you are on the TJ your belly height increased by 1" due to the larger tires resulting in a belly height of Y+1". Because you put on bigger tires you effectively reduced your wheelbase. You can't choose a belly height without choosing a tire size, and you can't choose a tire size without choosing a wheelbase -- and those all effect what you need of the other.

Again, this is based on ideals and what is proven to work good.

Bonus homework: After I was asked what tire size, wheelbase, and belly height I wanted it took me about a week to figure out the ratio concept and another week to understand what I wanted. I was caught up on why 37s were better than 40s. The cost of running one or the other is nearly identical, but once you build for one, you need to nearly redo the entire build to switch. Why are 37s better?
 
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Mike_H

Rust Belt Heavyweight
Supporting Member
Feb 28, 2017
3,973
Grand Rapids, MI, United States
Why are 37s better?
I'd guess uptravel and the extra 1.5" of bumpstop you need, all else being equal. I'm sure that can be overcome.

My other theory would be that it effectively shortens the wheelbase...if you need 37's to make the LJ act like the shorter wheelbase TJ on 35's, its stands to reason that 40's would keep "shortening" the wheelbase to the point where climbs would become tough...greater chance of roll over.
 
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toximus

toximus

TJ Addict
Mar 29, 2018
1,414
Northern WI
I'd guess uptravel and the extra 1.5" of bumpstop you need, all else being equal. I'm sure that can be overcome.

My other theory would be that it effectively shortens the wheelbase...if you need 37's to make the LJ act like the shorter wheelbase TJ on 35's, its stands to reason that 40's would keep "shortening" the wheelbase to the point where climbs would become tough...greater chance of roll over.
You are correct that both of those can be overcome. I think you'll see in later posts why the uptravel can only be the same with 40s if I were to ditch the body.
 

JMT

The Jeep Guy
Supporting Member
Ride of the Month Winner
Feb 27, 2017
7,318
Texas Hill Country
Firstly, you need to ask yourself what you are building for: mall crawling, hill killing, mudding, rock crawling -- the only wrong answer is the one where you lie to yourself. If you are building for strictly hill climbing the longest wheelbase you can shove under your Jeep is probably a fairly good idea. For desert racing the most travel you can fit in is a good idea. I'm chasing ideals for crawling with a touch of Ultra4 inspiration thrown in, which is based on a proven observed ratio of what works.

A TJ is ideal for what I am building for on 35s and a 100" wheelbase, this results in a breakover angle (determined by belly height of Y) of X.

An LJ takes a bit more to be able to run the same trails as that TJ. To have the same breakover angle of X in an LJ you must run 37" tires. But now if you are running the same belly skid as you are on the TJ your belly height increased by 1" due to the larger tires resulting in a belly height of Y+1". Because you put on bigger tires you effectively reduced your wheelbase. You can't choose a belly height without choosing a tire size, and you can't choose a tire size without choosing a wheelbase -- and those all effect what you need of the other.

Again, this is based on ideals and what is proven to work good.

Bonus homework: After I was asked what tire size, wheelbase, and belly height I wanted it took me about a week to figure out the ratio concept and another week to understand what I wanted. I was caught up on why 37s were better than 40s. The cost of running one or the other is nearly identical, but once you build for one, you need to nearly redo the entire build to switch. Why are 37s better?
Ok. First of all, curious what's best for rock crawling? I mean, what is the main thing I need to do to my Jeep to maximize crawl benefits (and stay on 33's)? I have a build plan and I feel like I've put my parts together carefully. But that's being challenged in my thinking.

Second, so you put bigger tires on, which effectively reduces your wheelbase. Why can't you extend your lower arms to increase the wheelbase back to where you want it? Or if you do that, are you losing the belly height you were wanting to achieve for that breakover angle?

On my build I wanted to go flat belly with a 3" SL and 1.25"BL on 33's, with JJ Rear upper and lowers to correct my pinion and re-center the rear wheels in the wheel well (no cutting on this end, not on this build). To me this sounds like the maximum thing I could do to my Jeep under said parameters. But I'm sure I'm missing something so take me to school!
 
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toximus

toximus

TJ Addict
Mar 29, 2018
1,414
Northern WI
I am still learning too. I do not have all of the answers but I'll answer your questions the best that I can.

Ok. First of all, curious what's best for rock crawling?
Only you can answer this to be sure. Observe what works well in the areas you wheel, ask what works well in areas you plan to go.

I mean, what is the main thing I need to do to my Jeep to maximize crawl benefits (and stay on 33's)? I have a build plan and I feel like I've put my parts together carefully. But that's being challenged in my thinking.
Balance. Balance your build to focus on everything as a whole rather than "the main thing". To correctly answer your first question of what works best for rock crawling you need to stop putting limitations on your build and in your thinking. Dream big and consider everything. After you answer the first question go back and add in those limitations. Do you want a full body (or buggy)? Do you want to stay with 33s because they're easier to change a flat? Do you have budget constraints? Do you want creature comforts for the drive home? Can you get inside a Jeep that's lifted more than a few inches? Do you need a rear seat? Again, no wrong answers here but don't needlessly limit yourself either.

I previously built for 33s and 35s on this Jeep following the general group hivemind of what works well. And those builds where alright. If I didn't like observing what works well and building so much I would have stopped at 35s and been satisfied.

Second, so you put bigger tires on, which effectively reduces your wheelbase. Why can't you extend your lower arms to increase the wheelbase back to where you want it? Or if you do that, are you losing the belly height you were wanting to achieve for that breakover angle?
The biggest reason why you can't simply extend the arms to get wheelbase back is because you're going to mess up your geometry. Bad geometry can commonly show itself in poor braking and poor climbing ability. If I build my geometry for 37s and extended the wheelbase slightly (all other factors being nonexistent for this discussion) for 40s the Jeep would not climb as well.
 
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