Talk me out of 37s

PNW_LJ

PNW_LJ

Nut-Swing Salesman
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Okay so I know 37s are widely accepted as a huge step up in cost and time to build well but hear me out here. I think what I have laid out as a build plan is reasonable but would like to hear your guys' thoughts before I plop down the big coinz.

What the build is going to look like:

04 LJ
42RLE
Savvy midarm
Highline fenders
Outboarded shocks
JK or JT axle swap w/ 5.38s and ARBs
37s


My initial build plan was to go with the standard 35s build with the savvy midarm and HP30 swap, however, I know I will likely want 37s in the future so might as well do it right the 1st time to avoid buying new axles/lockers/driveshafts/truss etc a 2nd time. With the LJ's worse geometry compared to a TJ, I think 37s are the right tire to help it compete with JKs on 40s that I will be wheeling with. The LJ wheelbase and the increased width/strength of JK/JL/JT axles are just right for 37s as well, IMO.

Yes, I'm mostly aware of the work that has to be done for this swap. Cutting off and welding on basically all new axle bracketry, track bar mounts, steering etc. I've never done an axle swap before myself, but I've done enough work around cars that I think I could figure it out with enough hours spent welding, cycling suspension, cutting off, and rewelding. 😅


My questions are:

1. Does anyone have direct experience with an axle swap like this? How much of a PITA was it to build everything the right way, minimizing bump steer/flexsteer etc?

2. Has anyone done a JL/JT axle swap specifically? They're way beefier than JK axles, but no one offers a swap truss kit for JL axles into TJ as of yet.

3. How bad are the 37s with 5.38s and 4.0 as a daily driver?


So let me know whether this is reasonable or if I'm talking out of my rear end :ROFLMAO:. Thanks in advance!
 
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Mike_H said:
When you say JL/JT axles are substantially stronger than JK axles, what are you basing that on? Do they have larger ball joints?
Click to expand...

If I recall correctly, they have stronger Cs and axle tubes (both of which were weak points on the JK axles). Axle shafts are different too. Ball joints I'm not too sure, but definitely something to consider.
 
Mike_H said:
When you say JL/JT axles are substantially stronger than JK axles, what are you basing that on? Do they have larger ball joints?
Click to expand...

Maybe @kmas0n can chime in. He’s using those axles on his build and I know he’s explained why they’re a good choice. I just can’t remember @PNW_LJ
 
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Its really the ball joints that are the common failure for 37's on half ton axles. I've thought that an older, kingpin Dana 44 would be up to 37s, but I don't know that there is a ball joint out there for a Dana 44 axle that is going to last on 37's. If you don't mind replacing them once a season...it will probably work out for you.
 
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Mike_H said:
Its really the ball joints that are the common failure for 37's on half ton axles. I've thought that an older, kingpin Dana 44 would be up to 37s, but I don't know that there is a ball joint out there for a Dana 44 axle that is going to last on 37's. If you don't mind replacing them once a season...it will probably work out for you.
Click to expand...

That's a very good point. I wonder how they hold up with all those heavy ass JLs and JTs on 37s. Maybe they just never go offroad? 😜
 
Mine is similar to your build, except I went with aftermarket axles. I have a Currie 60 rear, 44 front, 5.38. So not sure if the JL axles will be up to the task. Other than that, with the mid arm and 4" springs, there was a bit of trimming to do. I went with hi lines in the front.

I went with the 12.5" wide tires figuring I may already be pushing my luck with the Currie 44 in front. I was also having issues with losing a bead. The hi lines helped some, but ended up going with beadlocks.

LJ.jpg
 
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Jamison C said:
Maybe @kmas0n can chime in. He’s using those axles on his build and I know he’s explained why they’re a good choice. I just can’t remember @PNW_LJ
Click to expand...

The Factory ballpoints are still weak on the M210/M220 Axles, largely because the internals are plastic. Now the axles have been out 5 years, there is a ton of aftermarket options that are much more robust. M210 or M220 refers to the ring gear size in MM. Just from observation, the rear axles are pretty tough and lots of folks hammering on the while running 37's on jeeps weighing 5k+ and having twice the HP of a TJ. The front axle is a little more problematic, the FAD is a weak point, but not one that fails often. There will be some asshole post after this showing a M210 broken housing, but its pretty infrequent and almost always after doing something stupid. Axle shaft u joints are another weak point and I've seen them fail without much drama, but again, lots of aftermarket options.
I wouldn't (and don't) hesitate to run 37's on factory JL/JT axles. If I were going bigger, I would start considering chromoly shafts or 60s

Its possible to break anything.
In the HD world people bolt 3.0 shocks on their truck and bend one- ton housings.... while sending 8 thousand pounds of truck through the whoops at 60 mph.
 
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suicideking said:
Mine is similar to your build, except I went with aftermarket axles. I have a Currie 60 rear, 44 front, 5.38. So not sure if the JL axles will be up to the task. Other than that, with the mid arm and 4" springs, there was a bit of trimming to do. I went with hi lines in the front.

I went with the 12.5" wide tires figuring I may already be pushing my luck with the Currie 44 in front. I was also having issues with losing a bead. The hi lines helped some, but ended up going with beadlocks.

View attachment 402773
Click to expand...

Love your rig man! That is scary close to how I would like to set mine up. How's it do on city/highway with that setup?
 
kmas0n said:
The Factory ballpoints are still weak on the M210/M220 Axles, largely because the internals are plastic. Now the axles have been out 5 years, there is a ton of aftermarket options that are much more robust. M210 or M220 refers to the ring gear size in MM. Just from observation, the rear axles are pretty tough and lots of folks hammering on the while running 37's on jeeps weighing 5k+ and having twice the HP of a TJ. The front axle is a little more problematic, the FAD is a weak point, but not one that fails often. There will be some asshole post after this showing a M210 broken housing, but its pretty infrequent and almost always after doing something stupid. Axle shaft u joints are another weak point and I've seen them fail without much drama, but again, lots of aftermarket options.
I wouldn't (and don't) hesitate to run 37's on factory JL/JT axles. If I were going bigger, I would start considering chromoly shafts or 60s

Its possible to break anything.
In the HD world people bolt 3.0 shocks on their truck and bend one- ton housings.... while sending 8 thousand pounds of truck through the whoops at 60 mph.
Click to expand...

Right, thanks for chiming in! What ball joints are you running? I hear people having good luck with the dynatrac HDs.
 
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