My 2002 Tahoe has had a front end whine for quite some time. I originally thought it was the transfer case so I put a reman one in last weekend. Now the front and rear drive shafts spin freely of each other in 2wd (they were coupled 100% of the time on the old one), but I still have a whine. When I shift into 4wd, the noise goes away and comes back as soon as I shift back into 2wd. It only seems to whine the worst at about 45-55mph at a steady speed. The whine changes depending on loading. Truck has 312,000 on it and a junkyard front end (I hope this isn’t the culprit but I suspect it is). Any insight would be greatly appreciated.