AWD Problem

Several months ago I posted a problem with my AWD. While accelerating the truck felt like a bad miss in the engine but it was in the driveline. It would not do it in 4wd or 2wd. Since I was out of warranty I let it go and did not use the awd. It was time for the transfer case fluid change and when I drained the case the fluid was black. Refilled with Autotrack II (blue fluid) and now the awd works perfectly. This is my first electric/electronic transfer case. Anyone else experience this?