The guide rod controls the front to back movement of the lower control arm while under braking and acceleration. The guide rod mount is connected to the LCA and to the frame of the car. A proper installation of guide rod mounts would include an alignment.

The mounting point of the guide rod to the frame of the car should also be inspected. This is an area subject to cracking of the welded connection point. I had to have this done on my previous 300D. The crack will make noise similar to what you are describing.

If the frame connectors are securely welded, there are numerous other points that the can make noise on the front end of the 123 and 126 chassis. Sometimes you need to get the car onto an alignment rack and find a really good front end guy that will take the time to diagnois the noise and condition of the front end.

The LCA bushings get a fair amount of abuse on these cars and can be overlooked if the alignment guy is not an MB specialist.

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84 300DT Puke Yellow. Totalled after 438,000
84 300DT Orient Red. 169,000 (actual mileage may vary)
2002 Explorer EB (wife's)