Onomatopoeias are very subjective, and depend entirely on the sound, to say nothing of the different interpretations in different languages for the same sound. So bear in mind that any answer given is going to be subjective to one's own experience.
You might get a "creaking" noise, if the elevator is sticking and the metal parts are trying, but failing, to move against one another. Or if the metal elevator is straining against the cables, or if the wire is being stretched.
"Creaking" works especially well, since it includes both the squeaking sound one might hear from old, rusty, unoiled cables, as well as the grating noise one would hear from the metal parts pushing and grinding against one another. Even moreso, since it also describes an object that is moving whilst making this sound (A creaking elevator could mean that it is making this sound while moving, both implying the sound and the difficulty with which it moves).