I have an 03 f150 4x4, when idling and foot off of brake in drive there is a squealing sound almost sounds like a brake pad wear indicator, but it is not because if I jack both rear wheels off the ground and put truck in neutral and rotatedriveshaft so that rear wheels rotate forward I can hear the squeal noise and sounds as though it is coming from the front of the transfer case or rear of transmission right in front of transfer case. Truck has 150,000 miles on it and has been serviced religiously including transfer and transmission. Any ideas?

 

Crawl under there and manhandle the driveshaft.