I got a tan HOOVER power drive upright from (I assume) the mid nineties. Problem is, the power drive only works in reverse. I have never had a power drive hoover, so I don't know how they function. When I recline the handle, and the machine is off, whether the power drive is set to on or off, the wheels stick, and don't turn normally. but will with extra force. In use, it propels in reverse, but not forward, whether the power drive is on or off. Does the power drive belt just need replacing, or what else? Thanks in advance!!