Transfer Case Service Intervals?

[c4cruiser]

I didn't see anything definite in my 99 Silverado owner's manual regarding the service interval for the Auto-Trac transfer case. My truck has 70K on it and I have not had the Auto-Trac fluid drained and refilled. I bought the truck new in July of 99 so it probably has the blue fluid as the factory fill.

 

Is there a specific service interval based on mileage for the transfer case and for the front diff?

[Valsport]

I service mine every 20k, but I recall seeing 25k as a suggested service interval. The last couple of times i've drained mine however, it has come out green...when it goes in blue im not sure what is going on??

[c4cruiser]

If there's brass xomponents (thrust washers??) inside the transfer case that may cause the color change. Don't know if aluminum may do that.

 

I just find it interesting that there is nothing specific in the owner's manual that shows a mileage or time interval for maintenance. Just check the fluid levels at regular intervals.