Has any one ever changed their transfer case fluid and found it to have the wrong fluid? I have a 2005 GMC Sierra 1500 with 61k and bought in new. Started having a loud grinding/popping noise anytime I put it in 4hi or 4low and made a turn. Took it to the dealer and they found that it had a yellow fluid (I think it was gear oil) instead of AUTO-TRAK II. I did change all the fluids at 50k except that one cause I didn't want to pay $30 just for fluid and had read in many posts that if not used heavily it can make it to 75k or more. Any ideas? I was thinking maybe it was a preservative or at the time that is was the color of AUTO-TRAK II.