I've spent more time looking at the forum, YouTube, Trainz Wiki-page (much out of date info) and doing web searches on how to fix things than running trains in this game! While there are some fairly decent info out there, there is a definite lack of uptodate How To's for this program. The Trainz - Content Creation tutorials are great but leave many unanswered questions. How do you replace an asset? How do you replace a truck, wheel, sound, a building, track, ground or ANYTHING in this game. From what I understand there are a content creator can use a developed asset (ie a locomotive bogie for instance), give the original makes credit and add it to your 3d creation. How? Is that a function of the 3d program or is it in the asset config file?
If you decide to replace a truck on a locomotive, it is done in the config file. Sometimes the truck will be floating above the track when you go into Trainz. This is solved by following the instructions in the following link. But first, you must scroll down to 'Fixing with Hack #7 – Enabling the ARN on TUME’s FP45 and adjusting the mesh height'. Then scroll down a little more to where it says 'BONUS MOD'. This will explain how to solve the problem of trucks floating above the tracks. Link:
https://n8phu.wordpress.com/fixing-with-hack/
EDIT:
I also recommend you download the tools on this website made by fellow Forum member shaneturner. These have come in handy for me when I'm installing stuff into TANE that ends up being faulty. There are a few faulty items that I've come across that these won't fix, but these fix most faulty content. The ones that I use most often is PM2IM, Images2TGA, Trainz Mesh Viewer 2, and AssetX. AssetX is a bit tricky to set up, but once you set it up, it will help you out
a lot.
http://trainz.shaneturner.co.uk/tutorials/index.php?page=pevsoft-trainz-tools
EDIT 2:
Allow me to explain the purpose of some of the programs I listed:
PM2IM:
In previous editions of Trainz PM, short for Progressive Mesh, were supported. Trainz no longer support PM meshes and have been replaced with IM, Indexed Mesh, meshes. If something you install uses PM meshes, it'll show up as faulty. This program turns the PM meshes into IM meshes, making them no longer faulty.
Image2TGA:
In Trainz, content uses .TEXTURE files. If you save that as a .cdp in a previous edition of Trainz and install it into a newer edition of Trainz, it'll show up as faulty saying something like '.txt file missing for .TEXTURE file'. Trainz cannot 'read' .TEXTURE files, making these faulty. This program converts the .TEXTURE files into .TGA, (TarGA) files, which will no longer make them faulty.
Trainz Mesh Viewer 2:
This is also handy also.
AssetX:
I've only scratched the surface with this program, so I'm not certain how much this can do, but it'll come in handy.