I personally don't have the manual 4wd shifter in my 150, i have the electronic garbage, but i will tell you from experience of several other 4wd vehicles that the T-case does not shift smooth and easy like you may think. It doesn't feel like shifting a manual trans, it takes a little effort to engage, especially if it hasn't been engaged in a while. shouldn't have to really yank on it though. You could crawl under there and just double check that nothing is binding. Does the truck have a body lift?? that could create binding issues.
you can shift 2hi to 4hi on the fly, assuming all 4 wheels are spinning the same speed (in other words if you are stuck and spinning the back wheels don't try to jam it in!!). I'm not a big fan of doing it, shifting while stopped is an easy way to avoid some wear and tear, but moving slowly may actually help in your case (pun intended haha) to free things up and help engage it. shifting to 4lo ALWAYS requires stopping, and trans in neutral. sometimes letting your foot off the brake and letting the truck roll slightly can help engage 4lo.
go find a grass or dirt field somewhere and spend some time shifting it, and drive around in 4hi and 4lo so your truck can "stretch" a little. 4wd will be much easier to engage the more often you do it.
Last edited by chad085; 10-18-2008 at 10:26 PM.