The 2003 Expedition I diagnosed today (3/14/13) with 30k miles had the same growl noise ~ also felt in the steering wheel when starting / stopping (SLOW SPEED) while turning. Owner was complaining that it was tires or front end. He said it sounded much like a tire rubbing the fender. Closer inspection revealed that it was the rear axle making the noise. I believe it is going to be related to the Posi Track rear axle clutch. Hope to dig in and find more next week when he returns.
Check my source link for a very interesting read on the issue.
this FORD TSB was posted on 9/15/2003.
03-19-8 STEERING - LIMITED SLIP AXLE CHATTER, SHUDDER, BINDING SENSATION, OR VIBRATION DURING LOW SPEED TURNS
VIBRATION - LIMITED SLIP AXLE CHATTER, SHUDDER, BINDING SENSATION, OR VIBRATION DURING LOW SPEED TURNS
AXLE - LIMITED SLIP AXLE CHATTER, SHUDDER, BINDING SENSATION, OR VIBRATION DURING LOW SPEED TURNS
FORD: 2003 EXPEDITION
LINCOLN: 2003 NAVIGATOR
Some 2003 Expedition/Navigator equipped with the 9.75" or 8.8" limited slip rear axle
may exhibit chatter, shudder, a binding sensation, or vibration during
low speed turns. The sensation may appear to originate from the front
axle, or the steering gear.
To service, first verify the condition. With the vehicle at cold
startup. Ensure that the vehicle is in 2WD, to isolate the rear axle.
Turn the wheel fully right (or fully left) and then accelerate the
vehicle. If the condition is verified to be in the rear axle, replace
the limited- slip clutch pack.