The belt tensioner on my ‘89 300SEL rattles when idling in Drive (about 600 rpm). The rattle disappears when in Neutral (about 750 rpm). Two questions:

1- Does the tensioner need replacing or should I just replace the tensioner shock absorber? I’m thinking if the tensioner is bad then the rattle should continue regardless of the slight rpm variation.
2- Is the drop in rpm normal when shifting into D from N?

TIA

__________________
Riadh
'89 560SL Rauchsilber
And what is good, Phaedrus, and what is not good -- Need we ask anyone to tell us these things?