Chrysler 300M strange noise

[CactusBill]

I have a 2000 Chrysler 300M with 97,200 worry free and trouble free miles…up until 3 weeks ago. I then noticed a dull knocking sound at low speeds in the front end near the firewall on the driver’s side. Had it checked out where I’ve had it serviced for several years and found that it was time to replace the struts, replace the right front inner tie rod, and replace all the bushings in the steering system. Had all that done and I still hear the dull knocking noise…like hard rubber knocking together. Repair shop checked it out again very, very thoroughly and still found nothing. They even replaced all the bushings again at no charge for parts or labor. Still hear the sound…mostly at low speeds over a less than smooth surface. Repair shop said that although the steering rack was fine…no leaks, noises, etc., that it should probably be replaced anyway. Since they say it’s fine I’m very reluctant to have it replaced since I’ve already spent $1,700 in the past 3 weeks and still hear the sound. I need to know what is causing the knocking noise, is it safe to drive, should I really replace the steering rack, and what it should cost if I do?