Several weeks ago I noticed a slight rattling noise while in 4wd. Mentioned it to the mechanic and he said it was nothing. After a weekend at the cabin and some snow fall, spending a lot of time in 4wd the rattle has become significantly worse. Also now there is an intermittent whistle/chirping noise in 2wd. Haven't had an issues with 4wd performance just loud. Any suggestions? Recently had 4 shocks and ball joints done. Truck is stock other than airdog II. thanks