Knocking sound while turning steering wheel when car is stationary

When the car is stationary, parked and off, I slightly turn the wheel from left to right back and forth and it makes a knocking sound, from somewhere in the steering. Also, the steering wheel does not lock in place after you turn off the car. I replaced both outer tie rod ends, which were completely shot, and the noise reduced by a lot. But it is still there, a knock. A lot quieter, but there. When you slightly turn the wheel back and forth while parked. I suspect it is either the rack and pinion or the intermediate shaft. But I would like a second opinion before I start taking things apart. Thanks.