I have a 2005 Chevy Silverado 1500HD w/ 4x4.I am getting a grinding noise when driving in first gear. When I tow a trailer, the grinding noise is louder. I tried to isolate the noise so I lifted my back tires onto some jacks. With the tires are off the ground I can't hear the grinding noise. The noise only happens when there is load on my tires. If I accelerate up to 55-60mph with the tires are off the ground, I get a bunch of noise from my transfer case. I am assuming the issue is my transfer case. I have changed the fluids in my transfer case, tranmission, front and read differential. I have also rebuilt my rear driveshaft. I can't figure out where the noise is coming from. I believe it's my transfer case or tranny. I took it to a mechanic any they stated it was coming from either the rear of the tranny ornear theinput shaft of the transfer case.
Has any one encountered a similar issue?

Does anyone have any suggestions where to purchase a good tranfer case (NP246)for a good price?

Has anyone purchased transfercases from http://www.monstertransmissions.com/?

 

David, is it still under warranty?