GMPartsGiant.com offers the wholesale prices for genuine 2018 Cadillac XTS parts. Parts like Automatic Transmission Reverse Clutch 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, LUXURY 4 DOOR SEDAN, PLATINUM 4 DOOR NOTCHBACK, PLATINUM 4 DOOR SEDAN, PREMIUM 4 DOOR NOTCHBACK.