4 wheel drive only (front vibration)

:frown: good evening folks !. tODAY LOTS OF FREEZING RAIN HERE IN OTTAWA I went to put it in 4 wheel drive and as soon as it ingage front vibration with pulling as if something is completely screwed up in the front end, I can also feel it in the steering as a pulling what the eck is that the vehicle feels like it wants to stop i first thought i had a flat tire, or that i hit something but nope! it is not even driveable..... seems like my truck is babied too much I am starting to have all kinds of problems only 85km 5,3 litres yukon xl 2000. Please help me in trying to understand... when put back in 2 wheel drive no more vibration. So ill keep it that way until I get some news from ya..Thanks.

I have the exact same problem with my 1994 C/K pickup. Did you ever find out what the problem was? I'm afraid to use it. Don't want it to stay like that when I shift back to 2WD.