Buying an 03 h2....Need help with the 4x4.

[love dodge]

The hummer is an 2003 with adventure package and with air ride.It has 99000 miles and never been in accident...But i drove it today and noted something weird on the 4x4.
When making a turn with the steering wheel crancked all the way either to the left or to the right the wheels feel like they "sticking" to the ground and the truck stops if i dont keep pressing the gas.I can even hear a "scrathing noise" coming from the rear wheels.
Is this normal on the h2's?
I use to own 4x4 trucks before and remember this had happened with it but when i had the truck on 4x4 hi...
Tomorrow he is going to bring the truck to my mechanic to take a look and depends on what it is i'll decide to buy or not...

Thanks a lot