Hummer bummer

I have a 2003 H2. I am having trouble getting it to shift back out of 4LO. It seems to shift into it OK, but when I try to shift back to 4HI it never quite makes it. One of the wheels stays in 4LO. I know this because it sounds different running own the road, and when turning one of the tires squeals because it is turning faster than the other.

I heard that many GM models had this trouble on their 4WD vehicles.

Is this a simple fix like lubricating some linkage, or should I pray for a winning lottery ticket?