I have an 03 Silveraddo Duramax. The t case was toast when I bought it. I had it rebuilt and thought all was fine. When I went to shift in to 4HI while driving there was lots of grinding/noise sounds like it is coming trom the T case. Spoke to a couple of mechanics and they said maybe front diff actuator was bad so bought a new one and installed it. Still the same problem. When sittling still it all engages fine and no noises at all even when going down the road. At low speed it will engage but wth a loud "clunk" at speed only griding. When I have it engaged and going down road can shift from 4HI to 2HI as long as I dont "unload" the front end. Any ideas on what my problem is?