1.0 atx transmission problems...

My aunt has an older style 3 cylinder(not sure of the year...) with a tranny that seems to have a ind of its own. At a constant speed, it sometimes will constantly switch between the passing and normal gears, and is very slow to shift. Under throttle, like when going up a hill or something similar, 3/4 of the time it will not downshift as it is supposed to. Could ths be a computer problem, or is it just dying of old age? (the latter seems likely, as the car is old and was determined to be worth $75 :loser: )

Thanks in advance for any and all help!