MTD 917-0800A Variable Speed Pulley AssyUSED ON THE FOLLOWING MODELS. 135-618-000 (1985) Lawn Tractor. 135-620-000 (1985) Lawn Tractor. 135-638-000 (1985) Lawn Tractor. 135-668-000 (1985) Lawn Tractor. 135-669-000 (1985) Lawn Tractor. 135-688-000 (1985) Lawn Tractor. 13618S (1985) Lawn Tractor. 13619S (1985) Lawn Tractor. 13705S (1985) Lawn Tractor. 136-610-000 (1986) Lawn Tractor. 136-611-000 (1986) Lawn Tractor..