trying to find a post about wheels moving

[Nicholas Menaker <72074.2716@compuserve.com>]

A while ago, there was a post about having a Quattro up in the air, and engaging
the gears.  The lister mentioned that not all four wheels moved when the gears
were engaged.  Is this correct?  I noticed the same thing when I had the
suspension done.  Car in the air, 2nd gear engaged and then the front wheels
were  spinning, but the right rear simply rotated a LITTLE bit.  Not much speed
at all.  I mentioned this to the mechanic, and he said that the wheels,
especially the rears needed weight on them in order to have grip, or to rotate. 

Any comments.  Any way to check to engagement, without snow, or sand or gravel.?

Thanks 
Nick out