Ok guys/gals im in need of some serious help, i have a 1983 Ford Bronco with 351 engine in it. About 1 month ago i took it out of town and when i returned i noticed a whistling sound coming from underneath, possibly somewhere in the drivetrain i thought, so i got underneath and greased everything i could visually see. The noise has progressivley gotton worse and now i have a VERY LOUD CLUNKING noise coming from underneath, my guess its coming from the transfer case area. I do not have the front driveline on so i know its not coming from the frontend, it seems as if it has slowed down the truck and rpm's also, it happens in fwd and reverse and in every gear. When im driving i can put my hand on the 4wd shifter and i can really feel it as if the clunking is connected to it somehow. All my u-joints seem tight and fine so im really lost on this one, can anybody help please!!!