Workers at a Fiat Chrysler Automobiles assembly plant in Detroit have resoundingly rejected a four-year tentative agreement between the UAW union and the automaker, further jeopardizing chances of approval nationwide. At UAW Local 7, whose workers make the Jeep Grand Cherokee and Dodge Durango at the Jefferson North Assembly Plant, 66 percent of the production workers who cast ballots voted against the contract and 77 percent of skilled trades workers voted against the deal.