I first heard it start about two or three weeks ago. it started when i would brake too hard. so i took a look at the brakes and the caliper pin was rusty so i loosened it up and it was fine for a day or too. then all of a sudden it started in the front like something was grinding. someone told me it was the transfer case. so i put in 4 wheel drive and it goes but then you really hear the grinding. how can i tell if its the transfer case or the front end where the drive shafts go into.

 

remove the front drive shaft and check the joints... then drive the truck without the shaft and see what noise, then engage the front and test (but no sahft to drive the axle).