Top-load advantages

The top-loader's spin cycle between washing and rinsing allows an extremely simple passive fabric softener dispenser, which operates through centrifugal force and gravity. Fabric softener, vinegar, or any other liquid rinse agent, is placed in a cup at the top of the agitator. It "rides along" during the wash cycle. When the spin cycle is engaged, the fabric softener is pulled up by a tapered cup and centrifugal force, where it collects in the top of the spinning agitator. Once the spin cycle is completed, centrifugal force no longer suspends the fabric softener and it falls through the center of the agitator to join the rinse water coming into the tub. The same objective must be accomplished by a solenoid valve or a pump, and associated timer controls and wiring, on a front loader.
A lint trap can also be built into the center of the agitator, or on the drum's walls, passively collecting lint from water forced through the agitator. Front-loaders tend to require separate pumps and plumbing to provide lint filters which are often mounted behind covers on the bottom of the machine.
Another advantage to the top loading design is the reliance on gravity to contain the water, rather than potentially trouble-prone or short-lived front door seals. Top loaders may require less periodic maintenance, since there is no need to clean a door seal or bellows, although a plastic tub may still require a periodic "maintenance wash" cycle (described below).
As with front-loading washers, clothing should not be packed tightly into a top-loading washer. Although wet fabric usually fits into a smaller space than dry fabric, a dense wad of fabric can restrict water circulation, resulting in poor soap distribution and incomplete rinsing. Extremely overloaded top-loading washers can either jam the motion of the agitator, overloading or damaging the motor or gearbox, burning drive belts, or tearing fabrics - many Whirlpool/Kenmore machines even have a mechanical "fuse" designed to break before the expensive motor is damaged. Extreme overloading can also push fabrics into the small gap between the underside of the agitator and the bottom of the wash basket, resulting in fabrics wrapped around the agitator shaft, possibly requiring agitator removal to unjam.
Some top-loading machines use mechanisms very similar to front-loading drum machines, and are described below.