I bought a 93 grand cherokee laredo with a v8 and all wheel drive. When I am going slow, parking or u turns and  the like, something in the front diff grabs and the wheels lock up. The guy I bought it from said it always did that and a lot of all wheel drives do so he never tried to fix it. It really is a problem for me cause it scares my daughter who is going to be driving it. If anyone can offer any direction I would appreciate it.  

full time all-wheel drive trucks or flanged hubs (w/o locking hubs) have this problem. nm you could do but convert it to locking hubs and keep them unlocked unless you need the 4wd..  

The wheels lock-up? Or there is just some binding going on?

Sounds like the diff in the transfer case isn't opperating correctly. You really shouldn't notice much of anything when turning with all wheel drive.

Replace the hubs? Wrong.  

Also, there might be something wrong with the front axle u-joints.

Jack up the car and spin the tire while someone turns the steering wheel lock to lock. It should be smooth and not make any noise or have any roughness in/around the axle and wheel bearing area.