I've been slowly working through changing some of the fluids on my recently acquired '98 Suburban, and got to the transfer case. Now, I had noticed that, in A4WD mode, it would chatter and such in sharp turns (like in a parking lot. Don't you just love maneuvering a Suburban in a parking lot). Even though the owner's manual said to use DexIII in the transfer case, I had heard rumors that the NV246 required a special fluid. So I researched it out and, sure enough, GM sells a blue "Autotrak II" fluid specifically designed for their automatic 4WD equipped transfer cases, including the NV246. So I bought some (@ ~$8+tax per quart) and went to change the fluid. Went to pull the fill plug and discovered that GM had installed an odd sized fill plug, so none of my existing adaptors would fit. Ended up grinding down a 3/8 in male socket adaptor to ~5/16" (officially 0.307 in square) and that fit just right in the fill plug. Pulled the fill plug and, sure enough, red fluid came dribbling out. Pulled the drain plug (regular 1/4" drive) and got the Dex III out. Refilled with the blue stuff and took it for a test drive. No more chattering in A4WD.