Hi ,
creating separate thread just for N Wheeled is great idea - hope this thread will be kind of “first aid” for everyone having issues with this 
Couple days ago I wrote to you about my issues. Thanks for your attention, my custom WheeledVehicleMovementComponentNW class is working:
Of course it is veeery early version and needs hundreds improvements, like damping etc.
In matter of fact I made it similar way to N Wheeled Vehicles - Showcase - Epic Developer Community Forums Just like Edson I removed some features, eg. Ackermann system and various differential types due to PhysX limitations.
Last time I didnt notice I lost my WheelHandler modified class due to Visual Studio crash - without that little piece of code engine didnt know theres sth to do with additional wheels and thats why my AMV had broken rear axles
Time for bad news - I dont know why, but I cant move forward/backward, steering works fine as it seen in the picture above. I thought theres something wrong with my model, but all bones are fixed properly. Moving the root to (0,0,0) or modifying engine/torque/transmission parameters gives nothing. I know theres simple gimmick to fix it, but for now I don`t have any idea 