mercecedes w210 e200 knock or bang noise along axil diffs ,propshaft and

Ihave mercedes w210 e200 the problem is that each time i apply the the foot break it come up with a bang knock underneath the car as passenger in the car can feel it as if one is been hit with a harmer in the tail bone. i think this problem is between the gear box ,propshaft or axile and diffrential. can sombody help.this problem sometime disappears and then comes back or is propshaft playing up .Big thanks to all who help

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