Re: Sound when turning
OK, just a thought (or maybe a WAG offered in the spirit of trying to help).
Could the rubbing be from scuffing of your front tires on the pavement? Do you have ESOF front locking hubs? I drove my van inadvertently with the front hubs engaged for a year. The 4x4 converter had installed ESOF hubs at my request (in return for my payment) but instead of using the oem electric modulated vacuum pump (big vacuum to engage them, less vacuum to keep them engaged), he just hooked the ESOF up to the unmodulated nearly infinitely variable, way too strong, serpentine belt-driven brake vacuum pump. (You have a diesel, so you have a vacuum pump.) Well over time, the pump sucked the hubs inward to the permanent locked position, breaking off the little plastic tabs (Ford 2007 ESOF hubs) that hold the hubs in the unlocked position, such that even when I manually turned the hubs back out to unlocked position, they were in fact still engaged.
Just for giggles, you may want to unlock your hubs and have someone drive your van forward or back a foot or two while you watch to see if the transfer case driveshaft to the front differential spins. If it does, your hubs are, in fact, engaged.
2002 E350 ext.; 160K; 7.3L; 4R100 (w/4x4 deep pan & filter); 4x4 conv. w/2007 F250/F350 coil frnt axle (oppos. dual Bilstein press. shocks cured DW) diff chg from 3.55 to 3.73 (bad!); BW1356 t.c. (bad!); LT265/70R17/E Michelin LTX M/S2; Engel MT60 Combi Fridge-Freezer; 4 BP 380J pv panels; Auragen 5kw AC gen. in top alt. position; Webasto Dual-Top; Voyager top. 1995 5.8L EB Bronco, bone stock.