Ford Repair: Ford, 1999 Eddie Bauer Expedition, Stutter, ford repair, eddie bauer

Question
The car seems to stutter under the following conditions:  on slight incline; wheel turned slightly; asking for a little power; colder weather.  If I come off the gas a little, it seems to smooth out.

My mechanic says it is stuck in 4WD all the time and that is a bit dangerous and that I need to take it to a transmission place to get it fixed.  He has no idea of the severity or the cost.

Does this answer seem plausable to you?  Is it dangerous to keep driving it stuck in 4WD?  If I do go for the repair option, any idea as to cost?

1999.  115,000 miles.  all light duty.

Answer
Hello and thanks for the question...I'll try to help.
 It does seem plausable. I would suggest that you do bring it to a transmission shop or to a Ford repair garage ASAP. Having it in 4 wheel drive all of the time will destroy your front tires, as well as not being safe.
Hope this helps,
Erik