My 98 F150 is acting weird when engaged in 4WD. When i turn left in 4wd the truck feels like its fighting something and doesn't want to accelerate. Any ideas on what it might be and cost of fix?

 

4wd is not meant to be used on pavement. It needs slip the front wheels and wont so the cv shafts will bind while trying to turn.

 

Sounds normal to me, and I have owned many Jeep 4X4's and they all did that. I know it is bad for the vehicle but I would have fun going to an empty parking lot with a girl at night, turning the wheel all the way, and letting the truck go in a circle in 4 wheel drive. Scared my dates to death when the Jeep would fight itself, especially when I told them the Jeep was falling apart and might explode. Great way to get rid of girls I didn't want to date again. Of course there was this redneck girl who laughed when I did the trick and said they all 4X4's do that. She was cool.
Don't worry about it, it only means your 4 wheel drive is working.