Problem: "85" 300SD, 170K. I have a rattle or knocking noise with some minor vibration from the front end between 45-60 mph. The vibration can be felt through the steering wheel. Sometimes the noise will go away by turning the steering wheel to the left or right. I've replaced shocks, idealer arm, balanced wheels and checked for visable problems such as worn bushings etc. I had the steering adjusted and it seemed to somewhat fix the problem, however that was very short-lived. Anyone have any ideas or suggestions or experienced anything like this?

Sounds like you might have a bad steering coupling. This goes between the steering shaft and the steering gearbox. Its purpose is to allow flexibility in the steering shaft and dampen noise coming up the shaft into the steering wheel.