I'm looking to get a good solid understanding of what goes in a 4x4 transfer case.

I've heard all three of these reccomended:
-ATF
-Grape Juice/Synthetic 75W-90
-GM AutoTrac II

And there are THREE different transfer cases:
-Electronic traction control (4 BUTTON, Used in 1500's)
-Manual shift (knob on the floor)
-Electronic shift (used in 3/4 and 1 ton's)

My dealer told me AutoTrac II for an electronic shift 2500HD (3 square buttons), so I put that in. I'm looking to know if I should be going back to the dealer tomorrow before I cause some damage...

Assuming we are talking about 2500HD and larger trucks, these use a 263XHD for the electronic shift and the manual shift use the 261 series.

Those t-cases specify use of Dex III or equiv. Autotrak fluid will work just fine though. The difference with the autotrak fluid is it has properties in it that work with the clutch packs used in them.

How many quarts of DexIII are needed for a transfer case fluid change? will most likely use Mobil 1 Synthetic ATF.

How many quarts of DexIII are needed for a transfer case fluid change? will most likely use Mobil 1 Synthetic ATF.

Its never simple. There are now THREE different options for trasnfer case fluid- even more than my previos post. As of now there is:

-ATF
-AutoTrak II
-GM Manual Transfer Case Fluid.

I have the part number for the new one, which is specifically called GM Manual Transfer Case Fluid. I went to the dealer about a week ago and they told me it was brand new, and they wouldnt have it for another week.

I'm gonna try Royal Purple ATF. Good/bad?

Any deccent syn ATF(or regular ATF) will work in the HD cases.

I liked mobil 1 and ran it in my trans and transfercase in both the 03 and the 06.

Ok....this is just my WAG. In a HD's transfer case the lube in there is just there to lubricate it. Its not as finicky as a auto trans that wants a pretty specific additive package to make it function well. The HD cases without the "auto trac" and other fun clutches and wierd things in there just want something to keep em lubed and also a lil bit of cooling. I would say the more slippery the better as long as its in the viscosity range that its designed for and it stands up the way its supposed to.

I think at the price it costs for the couple of quarts it takes it makes sense to use syn in the transfer case.

I have been running Royal Purple for 90K with no problems.

How many quarts of DexIII are needed for a transfer case fluid change? will most likely use Mobil 1 Synthetic ATF.

I just realized I didnt actually answer your question. About 2 quarts, mine look less than 2. I would have 3 on hand just in case.

Thanks schulte!

I changed my Allison and transfer case fluids at the same time...used Transynd in both (synthetic and Dex III compatible).

Plugs are soft (magnesium I believe) and need liquid pipe thread when re-installing (clean thread with a wire brush first)...torque is 15 lb ft. Use a 6 pt socket (instead of a 12 pt.).