1995 Mercedes Benz CAR IN REVERSE GEAR

PLEASE HELP. 1995 MERCEDES C220. WHEN CAR IS IN R GEAR IT WILL NOT ROLL BACK OR MOVE. HOWEVER WHEN I APPLY MORE GAS IE PRESS GAS PEDAL FURTHER DOWNWARDS THE CAR DOES REVERSE. THE OTHER GEARS WORK NORMALLY AND THE TRANSMISSION CHANGES NORMALLY. I THOUGHT IT WAS THE BRAKES, BUTIT WAS NOT, THERE IS NO NOISE WHEN I REVERSE.
IT FEELS HEAVY AS IF THE WHEELS ARE CONSTRICTED, BUT ALAS THE WHEELS MOVE FREELY WHEN LIFTED UP IN THE AIR. YES IT IS BACK WHEEL DRIVE

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IT AS YOUR SERVICES ARE PROFESSIONAL. AND YOU DESERVE FOR YOUR HARD WORK. THANK YOU!