Transmission housing: 41-86 4-speed Big Twin (NU). Trapdoor: 80-92 5-speed Big Twin (Excl. Dyna); 93-94 FXR; 93-06 Softail; 99-06 FLT/Touring; 99-05 5-speed Dyna (NU). Primary cover: 86-06 Softail;