I think my original post was a bit misunderstood. I know how to shift in and out of 4 wheel drive. I've done it many times. I've even had the trasfer case "thunk" before. This is the first time I've heard the grinding noise. I assumed that I was going too fast and it didn't "catch". My assumption was that the grinding was most likely caused by the hubs. I was just posting to see if anyone thought it was worse than that. Sounds like it wasn't that big of a deal, but I'll watch my speed a little closer next time. I know it's best to come to a complete stop, but sometimes that's not practical. I happened to be on I-70 going up the pass to the Eisenhower tunnel. The folks behind me wouldn't have been too happy if I'd have stopped to shift into 4WD.