Hummer H3

My hummer h3 gets stuck when I turn the  steering wheel  
almost all the way like when I need to back up and turn to
pull out or to just take a sharp turn to drive in to a parking
it slowly comes to a stop and I have to give it a lot of gas
to make it move almost like in forcing it what helps is I put
the hummer in neutral then put the 4+4 on till I hear the
click the take it back off till it clicks again and then park
then I can drive forward or backward while going it it not
slowing down and me having to give it has it's nice and
smooth but the problem comes back almost emedietly I
need help it suck not being able to pull in and out off
pairking with me having to give it lots of gas and forcing it
to go help pleas.