I am preparing to do a fluid change on my 04 Silverado. I plan on doing the tranny, both diffs and the transfer case. I am going to use synthetic oils and lubes but the manufacturer has no recommendation for my transfer case (NVG 246-NP8). I have the push button 4WD. They list a GM part number (12378508) for this transfer case. I tried looking the part number up online but got no definitive answers. Any thoughts on this? I was going to see if there was a tag on the transfer case to see what it says for lube. Thanks.