select trac maybe having problem....help

This is my first 4x4 so please bear with me.......when getting out of 4wd should I have to put it in reverse for it to go back to 2wd? If I don't, I get a groaning noise for the driveline.

Also, whats the best fluid I should put in the transfer case?

Coming out of low-range you might need to back up, but just going into and out of high range 4WD is supposed to be "shift-on-the-fly," which means you can pop in and out while cruising down the highway (I think they say 55 MPH or lower, but I've done it at 60). It may take a few seconds for the shift to take place, but it should happen.

Groaning does not sound normal. Perhaps checking adjustment on the transfer case shift linkage is a place to start.

These symptoms can occur if your tire sizes are mismatched, either by wear or inflation (or, of course, if they're actually not the same brand and type). Make sure you rotate your tires regularly to equalize the wear.