well, for a Maytag, just slide a board in there and apply pressure to the motor, you will see a significant increase in wash action...spin too...
slippage for a ramp up during spin is one thing, once high speed is achieved, if slippage still happens, you not getting full use of the torque....
many machines used a clutch belt slip type of mechanism...ex.WCI-Frigidaire, even Speed Queens use a idler pulley/spring setup.....they have the potential to slip...
a good example of this is reaching in and grabbing the agitator, and being able to stop it, yet the motor will still spin....
now for machines like a Ge FilterFlo, Kenmore/Whirlpool, 1-18, for example, those belts are fastened tight, and bolted in place.....these mechanisms do not 'give in' to the load....they will power through any load, and again, clutching is only for spin ramp up....a better mechanism locks it in place for full torque, wash or spin...
I added a tighter spring to my SQ, and an extra to the Maytag...tighter tension, better grip!....