My 97 EB w AWD also growls a little too. Try removing the front driveshaft
and listening again. Mine is quiet wo the front shaft installed which
indicated to me that the AWD TC is the culprit. It has 120k miles but
appears in good condition! But beware, the transmission 'Park Position" will
not hold and the car will on a slope wo the front shaft.
R&Ring the AWD Case looks straightforward  in my Ford CD but the top
mounting bolts look difficult to get at. Maybe someone else can help here.
Jerry, Kingston WA

The front driveshaft is the most common front end problem on the AWD.  I
believe you have a constant velocity joint on the transfer case side of the
driveshaft like my 99.  This CV  joint is what usually fails on the
driveshaft, and is sometimes hard to diagnose.  It can sound like a transfer
case issue because it is  bolted right up to it.

Best thing is to yank out the front driveshaft and examine the u joint and CV
joint carefully.
While that's off, you can put the front wheels in the air and check the front
axle/wheel bearings for noise  / roughness.

You might want to try something simple like lubricating your rear U-Joint.
My 97 AWD was also making some noises that I thought were coming from the
front - ended up being the rear U-Joint...

Chris

I am hearing a growling noise coming from the front end whenever the
vehicle is rolling.  I suspect it is the transfer case since it was
worked on in the past.  How can i diagnose the problem myself?   And
where can I find instructions on how to R&R the transfer case if need
be?

Thanx