My perfectly running 2006 Porsche Cayenne Turbo S was shifting 110% fine. I had pulled over to the side of the road put reverse and backed up about 100 feet, the second I let off the gas in reverse the truck came to a stop fairly quickly like I applied the brakes with a medium amount of effort. And there I sat stuck. The transmission completely locked up and will not move in reverse at all whatsoever not even if the truck is off, you can't even tow it or push it backwards, It will pull forward though but it will only drive forward about 1 foot before it locks up.

Has anybody ever heard of this???

 

Sounds like your transmission is shot. Had that happen to me in my old Lexus when its transmission failed.

 

In a 4-wheel Drive vehicle it could be a couple of things. Obviously you need it flat bedded to your mechanic/dealer for evaluation. They'll let you know whether it's a transfer case, transmission or something out of alignment. Just don't force it so something additional happens.

 

A transfer case motor that is misbehaving can cause such symptoms.

 

great advice with this and to add I had a similar thing happen to me in my pickup truck rear wheels locked up on me and spun me sideways, after coming to a stop I have able to drive off I chewed up a few teeth in my rear diff. Hopefully its not your transmission

 

So... What was the issue?