Green’s Dictionary of Slang

pulley n.¹

a thief’s accomplice, usu. a female one.

1857		‘Ducange Anglicus’ Vulgar Tongue 28: rogue n. Thief. ‘Rogue and Pulley.’ A man and woman going out to rob gentlemen.
1864, 1867, 1870		Hotten Sl. Dict.
1869		Australiasian (Melbourne) 17 July 8/5: A pulley is a confederate.

SE in slang uses

In phrases

off one’s pulley (adj.) [? fallen off]

insane, eccentric.

1996

H. Roth From Bondage 114: When he let out that yell, I thought he had gone completely off his pulley.