Are you talking about Radio suppression .
Are you talking about the radio suppression sping steel as you remove the wheel bearing cap? If these are the ones you speak about I think they were used to keep noise out of your radio reception as it keeps a constant ground to your tires. I don't have them on my diesel. They might have come with them, but radio reception is great without them. I could see their purpose if this was a gasoline car with a typical ignition system. On a diesel I see no purpose for them.
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'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan