Built with GM’s engineering expertise, ACDelco and OEM GM parts are factory original equipment replacement parts for your Chevy, Buick, Cadillac, GMC, Saturn, Pontiac, Oldsmobile or Hummer. Every ACDelco and OEM GM part is rigidly held to federal safety and quality standards and is guaranteed by GM Replacement Parts Limited Warranty. You can trust GM Genuine Parts when ordering this Rear Main Seal for your 1988-1991 vehicle. GM Parts & Accessories Limited Warranty.