Hard to steer at low speeds.

My 2000 silverado seeems like it is stuck in 4wd or something...at really low speeds (ie. turning into a parking space) the steering feels weird, almost like it is stuck in 4wd, it seems to stop moving unless you give it a stab on the gas pedal. I have the same problem when making a three point turn in a driveway. Any ideas?? Oh I should mention it is an extended cab shortbed with the Auto 4wd.

It could also be the power steering pump. Try to turn the wheels while not moving at all. If the pump is working well, it should be easy to turn. Also, check the pump fluid level.