GMPartsGiant.com offers the wholesale prices for genuine 2018 Cadillac XTS parts. Parts like Automatic Transmission Input, Output And Reaction Gearset are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 6 Cyl 3.6L. Model Code: 4 DOOR NOTCHBACK, LUXURY 4 DOOR NOTCHBACK, PLATINUM 4 DOOR NOTCHBACK, PREMIUM 4 DOOR NOTCHBACK.