GMPartsGiant.com offers the wholesale prices for genuine 2015 Cadillac CTS Sedan parts. Parts like Automatic Transmission Assembly are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 4 Cyl 2.0L, 6 Cyl 3.6L. Model Code: 4 DOOR PERFORMANCE SEDAN, 4 DOOR PREMIUM SEDAN, 4 DOOR SEDAN.