A few weeks ago in the 30 or so inchs of snow we recieved my truck seemed to hiccup from time to time in third gear at 20-30mph in 4WD Hi. It would then continue fine for 5 or 10 min. then do it again. It did not do it in second gear and will not do it at any speed in 2wd. I have changed both transfer case fluid and gear oil in the past year. Tonight driving home in 4WD Hi it did not happen again at any speed up to 45 mph in any gear. What suggestions or opinions does anyone have?

Thanks in advance for your help!