A drive train assembly for use in powered vehicles or trailers having at least one axle of driving wheels. The assembly includes a coupling mechanism coupling the engine of the vehicle and the driving wheels. The coupling mechanism is activatable between a first and a second state, wherein in the first state the engine and driving wheels are mechanically uncoupled and in the second state the engine is mechanically coupled to the driving wheels. When the driving wheels are rotated by the vehicle or trailer being towed and the engine turned off the coupling mechanism ensures that no parts of the drive train assembly do not rotate and are therefore damaged due to lack of lubrication. Two embodiments are disclosed, one with the coupling (138) in the transfer box (110), and in the second embodiment the coupling is in the wheel hub assembly. Also disclosed is an oil pump assembly driven by the wheels rather than the drive train to provide some lubrication when the wheels are rotating and the engine is off.