I have been having a problem with the steering when turning sharp left/right corners from a dead stop. There is a rumbling sound and the steering wheel shimmeys. The sound is similar to a flat front tire while turning. There is no belt squeel, nor is there the typical howl for a low or failing power steering pump and it is not the clicking sound of a wheel joint going bad. Once I gain speed everything seems OK.

Is this a bad power steering pump, slipping belt or ?

 

sounds like your rack is going out.

 

I found that the grinding sound went away when the 4wd was engeged. Was advised to change the fluid in the transfer case because was sticking within the limited slip. Was told to use a synthetic oil - GM Auto-Trak ll. Two quarts solved the problem.