4 wheel drive question

The other day i took my '93 Yukon 2 door off roading for the first time and since this is my first 4x4 Im not really sure exactly how it should feel. However I did notice that the rear tires were spining and not the fronts. It did shift into low but I still dont think that the front tires were under power. I heard that the Front Axle 4wd Shift Actuator is a problem in these trucks. Do you guys think this could be the problem or do you know of a way to test it that doesnt include putting the truck on a lift or jack stands and seeing if the fron wheels are powered. Thanks in advance.