Hi, last winter I started to get a really loud and hard thumping sound from somewhere below my driver's seat. I took my truck into my school mechanic and he used his stethoscope and said there was a lot of vibration and sound coming from my transfer case when we lifted all wheels off the ground and ran it in 4x4 high and low. I bought a used transfer case and just wanted to know if anyone would know the specific issue before I go and replace the whole thing. Thanks.