So, some of you may recall the rear end issue with my truck.  I want to
try out the 4WD though.  Is there a safe way to test it so that if it
isn't a good match, I won't blow the transfer case.

Now, I had the rear end professionally done.  But, that doesn't mean
the right front axle gears are in place.  I tried setting the hubs and
putting it in 4wd the other day, and didn't even drive a whole foot.  
It creaked around the undercarriage and the front wheels shook a
little.  Is this normal?  Of course, I immediately stopped and took it
out of 4wd.