Green’s Dictionary of Slang

1. a solid-top car.

1928		San Bernadino Co. Sun (CA) 25 Mar. 41/1: Shed — a closed car. Front room — a sedan [...] Breezer — an open car.
1931		Irwin Amer. Tramp and Und. Sl. 168: Shed.–A sedan, coupe or other enclosed automobile, and widely used by automobile thieves.
1950		Goldin et al. DAUL 191/1: Shed. A closed car.

2. (US Und.) any form of depot or terminus, esp. of trains.

1940		D. Maurer Big Con 205: I [...] beat it to the shed and bought my ticket.
1981		E. Bunker Little Boy Blue (1995) 217: We work the sheds, the train station and bus depot.

3. a run-down car.

2001		OnLine Dict. of Playground Sl. 🌐 shed n. A very poorly maintained motor vehicle.
2003		N. Griffiths Stump 9: Yeh don’t send two of yer best boys off on a straightener in a fuckin shed like this, lar.