Black Coupling (92) 1-3/8", Passenger-Side (Old Style Configuration). 1-3/8" Top Shaft (Gearbox-End) and 1-1/2" Bottom Shaft (Brush-End). This coupling is an Older Style Coupling used on Galvanized frame systems. "Newer-Style" Aluminum frame systems use 1-7/16" Couplings (#766-2000) and Reducers.