Transfer case fluid change

[weo38]

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.

[taber.gmc]

I had the same problem with my 2000 GMC Sierra. The manual had no recommendations for the transfer case. I called a dealership, and they told me to use Dexron III (Transmission Fluid). On the other hand, our transfer case on the Duramax has to use super expensive GM Transfer Case lube.

[shadams]

Can vary depending on type of t/case. If you want to PM me the last 8 of your VIN I can tell you which. Some use transmission fluid, some use what GM calls Autotrac fluid, and some use manual transmission/transfer case fluid.

DOH! See you listed you case, hold on.

OK, the fluid part # you listed is for Autotrak-II fluid which goes in that t/case. Is that the info you wanted?

[weo38]

shadams here is the last 8 of my vin just in case my assumptions were wrong: 4Z273410

[howpeculiar]

The blue transfer case fluid can be sourced at GM, you should need 2qt, and it isn't expensive.

[weo38]

Thanks for the info. Now that I have that cleared up how do I tell which ring gear I have in the rear end? My truck has 3.73 ratio. And how do I tell which tranny pan i have on my truck deep or shallow and if it is a reusable gasket?

[GMCSonoma]

You have the 8.6" rear diff with Posi & 3.73 ratio...both diffs use 75w90 synthetic...

Your transmission is a deep pan...oe# for the transmission service kit is# 24208576.

You will need two liters of the Auto Trac fluid for the tcase....#12378508

[Headymusk]

In my "2001 Diesel Supplement" manual it says for "manual transfer case" you should use Dexron III. For an "automatic transfer case" use Auto-Trak II. I was confused at first then after a couple of days of research I found out that the meaning of automatic trasfer case was if you have a 'Auto 4X4" button in your truck. In which I do not recall ever seeing one in a full size truck. I have however had one in my wife's 2001 ZR2 Blazer. Weather this is differnt because my truck is a diesel, I have no idea, but manual is manual and automatic is automatic.

[thorin72]

I have one in my 2004 silverado 2500 hd.....so there are a few out there.

[BDANN]

Im brand new here but how do I obtain a detailed rpo list mainly i need to know what tranny, diffs, and tcase I have so I know what fluids and addatives to buy just bought a '06 silverado w/66000 miles and I want to change all fluids hopefully to synthetic