2010 ML350 AWD Towing

So AWD was a big factor in purchasing my ML350. So here's the question: If you put an AWD vehicle in park (turned off) do all the wheels lock?




With the parking brake set the back wheels (and hence the back axle) will not turn therefor the front axle will not turn. (if one wheel turns the other has to turn the other way.
In general with the transmission in park and the parking break on three wheels need to loose almost all traction to slide/



