XJ axle swap/build

Rob D said:
Yeah, I have the same TnT truss. I have an F250 front this time. I have a 150 narrowed down to take TJ d44 inners now but it's too narrow for 37's with the wheels I have. I've got a 3.8 Atlas to make the crawling easier and 4.88's for now.
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Right on man! I hope to get an atlas sometime in the future.

Got the truss fitted to my axle today but couldn’t weld it on as my inner C’s aren’t welded on yet. Got the angles where I think they should be. The angle of my front drive shaft is 10-11 degrees and I have the pinion angle set to 10 degrees. Each C is set to 5-6 deg positive castor right now. My friend is going to weld them on with stainless or nickel rod and an arc welder. Hope to finish gearing the rear axle and weld the truss on next weekend.
62977246ec9cb4308c1f3e669bbe4b75.jpg



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Also I have a question for those of you who have done this before. With the angles I have with my pinion (10*) and inner C’s (5-6*), the truss is 3* from level. How much does this matter? Should I adjust lower my pinion angle to address this? Any input is welcome. Thanks in advance!


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I got mine mostly welded on Monday. Something I noticed in your pics. TnT says you need to trim 2 3/8" off the driver's side of the housing on the F250 housings. I thought about just trimming the truss like you did, but the problem is the lower control arm mount. It needs the housing trimmed so your not trying to weld the control arm mount to the cast iron housing. I didn't like trimming off part of the housing, but having the control arm mount welded to the housing will cause 2 issues. First, since only half of the mount will be on the housing (requiring half of the mount to be trimmed) and the other half on the tube, there will be a clearance issue with your control arm (it's not going to fit in the control arm mount). Second, I don't think the weld to the cast iron would be all that strong and may eventually tear off.

I have mine set up at 12 degrees of drive shaft angle and 7 degrees on the "C"s. I had to do a little trimming on the truss to make that work, but got 0 degrees on the spring pads at those settings. If you have a retaining bolt for your springs, that and the spring cup will keep the springs in place if it's not exactly at 0 degrees, as long as it's not off too much.
 
Rob D said:
I got mine mostly welded on Monday. Something I noticed in your pics. TnT says you need to trim 2 3/8" off the driver's side of the housing on the F250 housings. I thought about just trimming the truss like you did, but the problem is the lower control arm mount. It needs the housing trimmed so your not trying to weld the control arm mount to the cast iron housing. I didn't like trimming off part of the housing, but having the control arm mount welded to the housing will cause 2 issues. First, since only half of the mount will be on the housing (requiring half of the mount to be trimmed) and the other half on the tube, there will be a clearance issue with your control arm (it's not going to fit in the control arm mount). Second, I don't think the weld to the cast iron would be all that strong and may eventually tear off.



I have mine set up at 12 degrees of drive shaft angle and 7 degrees on the "C"s. I had to do a little trimming on the truss to make that work, but got 0 degrees on the spring pads at those settings. If you have a retaining bolt for your springs, that and the spring cup will keep the springs in place if it's not exactly at 0 degrees, as long as it's not off too much.
Click to expand...



I see what you’re saying about that. I haven’t looked far enough ahead to know how far apart the LC mounts need to be. Looking at it If I put the LC mounts outside of the housing would they be too far apart? I’m not sure if tires would contact the control arm with how far back from the knuckle they would be. I could be incorrect tho haha, there is probably something else I am forgetting that won’t clear
I think I might have to clearance the truss a bit more to get my angles better.


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DocTremp said:
Also I have a question for those of you who have done this before. With the angles I have with my pinion (10*) and inner C’s (5-6*), the truss is 3* from level. How much does this matter? Should I adjust lower my pinion angle to address this? Any input is welcome. Thanks in advance!


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Click to expand...

Truss not being perfectly level isn't a big deal at all. If its way off, yeah depending on any brackets you may be adding. I definitely wouldn't try to fix that and mess up your optimal pinion angle.
 
EricsXJ said:
Truss not being perfectly level isn't a big deal at all. If its way off, yeah depending on any brackets you may be adding. I definitely wouldn't try to fix that and mess up your optimal pinion angle.
Click to expand...



Thanks! I wish those were my welds. I bought the truss.
Thanks for clearing that up for me, I wasn’t sure but that’s the direction I was leaning. It’s about 3-4 degrees off level with the pinion at 13 degrees. Went with 13 as I did more research and I found that with a high pinion axle you want your pinion a degree or two above the drive line angle to compensate for when you apply torque to the axle?


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Finally finished the gearing of my rear diff. Got a pretty good pattern. Fixed the cut/turn to better angles. Kind of mocked up my UCA and Track bar mounts but need to get the axle under the Jeep before I do anything serious.
484f80313a4053b005339411dd181f9e.jpg



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DocTremp said:
Went with 13 as I did more research and I found that with a high pinion axle you want your pinion a degree or two above the drive line angle to compensate for when you apply torque to the axle?
Click to expand...

That usually applies when you are using leaf springs because the pinion angle will change due to axle wrap under load. I'm guessing for this front axle you are using links, so there shouldn't be any axle wrap (unless you have very loose or soft bushings) and even then it would be negligible.

Set your pinion and caster to where you want it, and put the truss to as level as possible.
 
EricsXJ said:
That usually applies when you are using leaf springs because the pinion angle will change due to axle wrap under load. I'm guessing for this front axle you are using links, so there shouldn't be any axle wrap (unless you have very loose or soft bushings) and even then it would be negligible.



Set your pinion and caster to where you want it, and put the truss to as level as possible.
Click to expand...



That makes a lot more sense, thanks for clearing that up for me!

I’ll be in Hawaii for two weeks so I won’t be able to get much done on this project. When I get back plan to get frame stiffeners on and mount the stinkyfab frame side brackets and crossmember mounted.


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Been working on prepping the Jeep for frame stiffeners over the weekend. Hopefully will have them burned in by the end of the week.

I am thinking of stretching the front a bit but after looking around on a few different forums I haven’t found a consensus on how much you can stretch before you run into issues with the track bar and steering. Any advice would be greatly appreciated!


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DocTremp said:
Been working on prepping the Jeep for frame stiffeners over the weekend. Hopefully will have them burned in by the end of the week.

I am thinking of stretching the front a bit but after looking around on a few different forums I haven’t found a consensus on how much you can stretch before you run into issues with the track bar and steering. Any advice would be greatly appreciated!


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Front stretch without moving anything is 2” max for sure. I found the pitman arm to be the first thing in the way after the trac bar.


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