Edited: Oups I don't have upload the good demo I reupload it again sorry.
The wheels joints code is based on the tractor demo code write by Julio.
Modified and integred in my system.
Here my last version and my last test.
In this version you have two vehicles exemple but it is possible to create many more models.
In this demo the vehicles is not the most good setuped I don't have take so much times to configure it better.
It is just a quick exemple to show how my implementation working.
The vehicle base is a compound objects and you can totaly create a custom vehicle in any axis and position.
http://orionx3d.googlepages.com/Basic_CustomCar3.zip
The code is present in the demo.
If Julio you need again some informations just to let's me know.
If you not need this code anymore I can edit the post and remove the code parts.