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Two inch square (Reese Hitch) receiver trailer hitches were dealer installed. It had no affect on the warranty if the dealer installed it. Some dealers also installed transmission oil coolers and motor oil coolers that were carried in service inventory that were used on factory built police cars as well as the weld in frame connected Reese hitch. If it was a bolt on two holes drilled in the bumper U-Haul quickie hitch that could adversely affect the warranty (and your car insurance; as most policies have a disclaimer about towing a trailer).