Interesting you ask because I replaced mine about two years ago, along with tensioner arm, pulley, and spring. I recently replaced my front crank seal and hub and upon reassembly, mine it rattling. This occurs when the bushing that bolts on either side gets worn out. For some reason, my bushing is worn out, although I suspect the shock itself is fine. My guess it that it was like this before, but I simply did not notice it until my head was in the bay checking everything after the last job I completed.

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1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000