Knocking sound

[Jensen]

My W202 C250TD with 128,000 miles is due a service in 800 miles by my indie. I,ve noticed a slight knocking sound that seems to be at the rear of the car, particularly when parking in the garage as I move over a slight step up in to the garage. Also sometimes at lower speed on some bumps.
Any ideas what this could be and typical cost?
Could this be a drop link, whatever that is.

Thanks

 

[Ellsy Tanners]

Possible a knocking from a shock absorber at that millege. Not too expensive or difficult to change!!