The dryer is always on top of a stacked laundry appliance since it is lighter than a washer full of water. If reversed, the machine would tip over. The dryer in your appliance uses a rubber belt attached to an electric motor that tumbles wet laundry in the drum. Belts eventually wear out or break, causing the drum to stop spinning. Buy a replacement at an appliance repair center or hardware store.
Slide the stack washer and dryer into the room to get behind the appliance. Thus, you can more easily disconnect the electrical cord and close the two valves where the washer hoses connect to the wall.
Disconnect the hoses from the rear of the appliance with a wrench or pliers, lowering the hoses into a bucket to drain.
Unscrew the metal panel on the back of the dryer and remove to gain access to the inside. The drive belt fits over the drum and around the drive shaft of the motor, with a spring-loaded pulley providing tension. If broken, the belt may have fallen inside the appliance. Cut the belt with scissors and pull it out of the dryer cabinet.
Slip a new belt onto the dryer drum and let the lower part of the belt hang below the drum.
Slide the belt between the pulley wheel and the bracket that holds the wheel in place, pulling the belt out the other side toward the electric motor. Push the pulley on its bracket backwards to release the tension, then install the belt on the groove in the motor shaft. Let go of the pulley to restore belt tension.
Ease the belt into the slot around the drum of the dryer, rotating the drum with your hand to guide the belt into position. Tug on the belt at the side of the drum to confirm the belt moves smoothly around the motor, through the pulley and around the drum, which will turn as you pull the belt if it is properly installed.
Attach the cover panel to the rear of the dryer with the screws.
Hook up the water hoses to the pipes on the washer and the wall valves. Dry your hands before plugging in the electrical cord.