Willing to pay anyone willing to teach parts replication

Generally when it comes to duplicating axles you need to do the following:

1. Either duplicate the 3D models of the parts you need in Blender, move them to the proper place and apply all transforms, make sure to not change the materials but make sure to rename your axle mesh (this method is useful if you want to modify these models) or in the Jbeam you can use the nodeMove modifier on the slot (if you don't want to modify the model, it's faster).
2. In Jbeam the first thing you need is making a slot for the second axle. You have to locate where the first axle slot is, it will look something like this: ["trailer_axle","trailer_axle", "Axle"], You have to modify it to include the second axle next to it. If you are using a modified model, just copy and paste this slot and edit with changed names, for example: ["trailer_axle_2","trailer_axle_2", "Second Axle"], If you are not modifying the model, you can use the nodeMove modifier to move a copy of the original axle to another place here: ["trailer_axle_2","trailer_axle_2", "Second Axle", {"nodeMove": {"x":0, "y":-0.4, "z":0}}], the number after y is the offset in meters you want to make for the new axle.
3. The second thing to do is making an edited copy of the original axle. Find the Jbeam file of the axle and work on a copy of it. You have to rename the names and slot to what you set earlier. The axle will have its own slots that you also need to rename. Do not change the order of the slots. If a slot has a nodeOffset modifier and you aren't using nodeMove, then you have to add the offset of your axle to the offset specified in nodeMove (this will set the position of the wheels and other similar parts). If you have edited models in Blender, rename flexbodies accordingly to how you renamed your own ones. You need to rename all the groups and nodes to have original names, and in the following sections rename the references to these nodes accordingly. If any nodes that aren't part of the axle are referenced, you need to find where these nodes are on the body relative to the original axle and change them to the nodes that are in the same position relative to your own one. Additionally, if you are working on a modified model without nodeMove, you also need to manually move all of the nodes to fit the position of the new axle.
4. Before adding any individual components of the axle, you have to double check if there are any references to the nodes of original axle in the body Jbeam. If there are, then you need to copy+paste them to your new axle Jbeam and change so they refer to the new axle and the positions of the nodes attaching to the axle are the same relative to the new one as to the old one (this is to keep the geometry the same, which is a key factor in suspension).
5. Adding individual components is mostly the same process as adding the main axle. You only need to be REALLY careful with the spindles (they will be called wheeldata). If you miss even the smallest detail there, there can be disastrous consequences. All the references to nodes, groups, wheels, etc. need to be renamed properly. Be also careful with the springs and shocks, rename nodes properly to avoid bad geometry. Brakes will be almost unchanged for the most part, not much to rename there. Remember that if you are working on an edited model instead of using nodeMove, you have to move all the nodes manually.
6. I assume the trailer uses custom wheels and tires, make sure to also copy+paste and edit these. Here you don't have to edit positions of anything since it's done by the nodeOffset you edited earlier.
7. Some extra tips: If your 2 axles are on a bogie, you can make second bogie instead of extending the existing one, that will be much easier. If something explodes, causes instability or behaves weird, you need to double check if you renamed everything properly, sometimes starting over is faster than locating and fixing the error. If you have texture issues, check the materials of the parts you edited. Always check the console, if there are any more errors than the trailer had originally then fix them immidiately because suspension is really sensitive to problems like this. You don't have to restart game after every change you make, as long as the mod you are working on is unpacked, you can reload it with ctrl+r and the changes will take place in real time. If you have too many mods while working on this, the game can be slow and unresponsive at times because it has too much to process, better disable most of your mods prior. To move nodes easier you can search for some automated tools on the forums, but they can be very sensitive to the syntax, you will have to make sure it's identical to the one in vanilla cars, counting even all the commas and spaces. If something else goes wrong, you can send a screenshot of the problem along with the Jbeam and someone will definitely help.

 

From what I see in these files you didn't actually rename anything at all other than the meshes. Please actually send the most up to date files with everything renamed properly. Also no offense but 2 hours is very little time for something like this.

 

You didn't rename anything with the wheels, I pointed out that it's really important in the spindles section, but the problem is in the main section too. If you are using some tool to rename automatically then I would really advise against it, for wheels you need to be really careful and do it manually. You also have to change the points where the new axle attaches to the frame, that also you need to do carefully by comparing the original node positions to new ones relative to the axles. And something I forgot about is the powertrain, you will have to remake it from scratch afterwards since simple copy+paste and editing won't work here.

 

C:\Program Files\Steam\steamapps\common\BeamNG.drive\content\vehicles\semi\semi_suspension_R.jbeam