The Dodge Diplomat is an American mid-size car made from 1977 to 1989. It is substantially identical to the Chrysler- and Plymouth-branded versions of Chrysler's M-body cars, including the Chrysler LeBaron and New Yorker Fifth Avenue and the Plymouth Gran Fury in the U.S. market and the Plymouth Caravelle in Canada. It was also sold in Mexico between 1980 and 1981 as the Dodge Dart, and in Colombia as the Dodge Coronet. The Diplomat was initially offered in a coupe and sedan. In 1978, station wagons were added as replacements for the departed full-size C-body Wagons.
The Diplomat was offered with a base 225 cu in (3.7 L) six-cylinder engine. In 318 cu in (5.2 L) V8 form and an optional 360 cu in (5.9 L)) Diplomat, along with its Plymouth Gran Fury/Caravelle twin, were widely favored as a police car both in the US and Canada. Aside from the 3-speed Torqueflite automatic transmission, manual transmission was available in some years and markets on six-cylinder and 318 engines; the 360s were automatic only.
The Diplomat name was originally used by Dodge on 2-door hardtop models from 1950 to 1954. It was also used on the export version of the DeSoto from 1946 through 1961. Between 1975 and 1977, The Diplomat name was also used on a trim package available on the Royal Monaco two-door hardtop.
Starting with the 1977 model year, the Diplomat became a full model line, rather than as the name of a particular body style. It was a longer, fancier upmarket version of the F-body Aspen. The chassis and mechanical components are identical, and doors and various other body panels are interchangeable.
The 1980 model year brought new exterior sheet metal for the Diplomat, although wagons were unchanged from the doors back. Manual transmissions were dropped. Following the demise of the Dodge St. Regis R-body in 1981, the Diplomat remained, becoming the largest sedan in the Dodge lineup, despite technically being a mid-size car. Dodge would not market another truly full-size car (at least based upon United States Environmental Protection Agency (EPA) passenger volume statistics) until the Monaco debuted as a 1990 model.
By 1981 Chrysler was switching to smaller front-wheel drive designs. However, its older and larger rear-wheel drive Dodge Diplomat (as well as the Chrysler LeBaron and Fifth Avenue) continued to sell. Chrysler's then executive vice president for manufacturing, Steve Sharf, met with officials at American Motors (AMC) to use the extra capacity at an assembly plant in Kenosha, Wisconsin to build the full-size cars. Chrysler's tooling was moved from St. Louis to Kenosha, and over the next two and a half years, about 250,000 Chrysler and Dodge models were built by AMC at a lower cost than Chrysler could. This relationship evolved into Chrysler's purchase of AMC in 1987.
In 1982, the coupe and station wagon were discontinued and Canada's Plymouth version of the Diplomat came south of the border. The Plymouth Caravelle was offered in the US as the Plymouth Gran Fury. 1983 was the last year for the Slant Six, and afterwards the only available engine was the 318-cid V8 with a two-barrel carburetor. A four-barrel 318 and a 360-cid V8 remained the optional engine choices for the police package.
For 1984, an upscale series was added to the American-market Diplomat, the SE. The SE used the Fifth Avenue's front end with its parking lights located above the headlights. The grille insert used thin vertical bars with a wide trim strip dividing the grille vertically as well as horizontally. The SE had more exterior trim and an interior that placed the SE between the Diplomat Salon and the Chrysler Fifth Avenue.
As the 1980s progressed, fewer private customers purchased the Diplomat, and the M-body was eventually dropped during the 1989 model year. One reason behind the drop-off in sales was fuel economy. Despite lower gas prices in the mid- to late-1980s and a 2.26:1 rear-end gear ratio, the Diplomat's carburated engine and lack of an overdrive gear on its TorqueFlite automatic transmission resulted in poor fuel economy compared with its larger competitors from Ford and General Motors, as evidenced by comparing the EPA estimates for 1986 models:
- Dodge Diplomat (5.2 L V8, 3-speed automatic): 16 city, 21 highway, 18 combined
- Chevrolet Caprice (5.0 L V8, 4-speed automatic with overdrive): 17 city, 25 highway, 20 combined
- Ford LTD Crown Victoria (5.0 L V8, 4-speed automatic with overdrive): 18 city, 26 highway, 21 combined
Late in the Diplomat's run, the car was subject to the federal "Gas Guzzler Tax."
Diplomats built from mid-1988 until the end of production were among the first Chrysler-built products to have a driver's side airbag as standard equipment, some two model years before the remainder of Chrysler's lineup (They were also among the only cars at the time to offer a tilt steering column with an airbag). Diplomats with airbags differed from earlier models in that they were also equipped with a padded, color-keyed knee blocker which extended out from beneath the instrument panel in front of the driver.
When the Diplomat and similar Plymouth Gran Fury were discontinued, it marked the last rear-wheel drive non-truck model (aside from the Dodge Viper) sold by the corporation until the Plymouth Prowler was introduced in 1997. The Diplomat's other rear-wheel drive sibling, the Chrysler Fifth Avenue, also ended production, but the nameplate was continued on a front-wheel drive chassis. In the Dodge lineup, the Monaco became the top-of-the-line sedan.