Transmission Fill Plugs

9 products

Transmission Fill Plugs for Harley-Davidson seal the oil fill and drain ports on your gearbox, keeping the correct fluid level inside while preventing contamination. Stocked by Iron City Motorcycles, an authorised Harley-Davidson dealer in Leeds, these plugs fit 45-inch Flatheads and four-speed Big Twin transmissions from 1936 to 1986. Colony leads the range with chrome, polished and OEM-style plugs, complemented by options from MCS, Samwel and Gardner-Westcott. A fresh fill plug with an intact O-ring or fibre washer stops the slow weeping that stains your garage floor and ensures your transmission oil stays clean and at the proper level. Browse the full range below.