Don't just visually check the boots. Check if the boot is open with your finger. The mechanic had my car twice and said there was no problem. I brought the car elsewhere and that mechanic also said the same thing with the car on the lift until he put his finger on the crack and found it was open and the boot contained no grease.
My half shafts sounded like dragging tin cans. Like this:

mb1985rearendnoise300dt.wav - 0.33MB

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1985 300D Turbo
"Evolution is God's way of giving upgrades" Francis Collins