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The Chrysler M-Body Was Dodge and Plymouth's Last Old School V8 Rear-Wheel Drive Gasp

In the 1980s Chrysler was Detroit's biggest champion of front-wheel drive. With a line-up made up almost entirely of K-car platform sedans, coupes, and their minivan and turbocharged derivatives, the nearly-broke automaker kept things simple and saved mega-bucks by refining its front-wheel drive engineering nearly across the board.

Dodge Diplomat coupe front view

The most visible exception to the Pentastar's FWD focus was the M-Body, a gaggle of generously-proportioned mid-size cars that ended up as the final rear-wheel drive hold-outs from Chrysler's body-on-frame era. Led by luminaries such as the Dodge Diplomat, the Chrysler Fifth Avenue, and the Plymouth Gran Fury, these square-looking stalwarts left a legacy of carnage on action movie screens for more than two decades before they were replaced by the Ford Crown Victoria as the easiest, and cheapest, sedans to power-slide and smash up during adrenaline-soaked chase sequences.

Dodge Diplomat Coupe covered in snow

Built from 1977 to 1989, this collection of Dodges, Chryslers, and Plymouths filled both police fleets and the driveways of traditional big car buyers seeking the last of Mopar's faded glory in the face of the small, econo-minded front-wheel drive saviors that pulled the mothership out of bankruptcy. They also present outside-the-box potential for classic car fans looking for a cheap, V8-powered project with surprising performance potential.

From F And R To M

At the end of the 1970s Chrysler was dealing with a debacle. Its F-body cars—the Plymouth Volare and Dodge Aspen—were its latest set of stylish mid-sizers that unfortunately also came with a host of quality problems that sealed their fate in the market.

1977 Dodge Diplomat coupe

There was hope on the horizon, however. In 1977, just one year after the F-body appeared, Chrysler introduced the Dodge Diplomat and the Chrysler LeBaron. These two vehicles rode on the M-platform, which was dimensionally and mechanically almost identical to the F-body, but with the virtue of having all of the bugs worked out. Even some body panels could be interchanged between the ostensibly 'different' automobiles. Available in both two-door and four-door editions (and eventually a wagon), the M-platform quickly replaced the F-body (which was dead by 1980) as well as the somewhat larger R-body (which lasted until 1981), giving Chrysler a single, do-everything big car chassis that could be shared across each of its divisions.

Dodge Diplomat coupe brochure

Originally, both the Diplomat and the LeBaron were aimed at higher-end customers as part of a plan to differentiate them from the Volare and the Aspen. This effort primarily applied to the exterior styling (which was initially quite conservative) and the interiors (which provided a longer list of comfort features and, for the time, improved fabrics and materials).

Dodge Diplomat wagon

Almost every model was built with the same 318 cubic inch V8 engine, which was good for roughly 145hp, but it was possible to 'trade down' to a 110 hp version of Chrysler's unkillable slant six until the 1984 model year. A 360 cubic inch V8 was also offered as an option, delivering a 10 hp boost over its smaller sibling, but it left the order sheet after only a few short years. A three-speed automatic was the most common gearbox, and some cars were built with a four-speed manual, which was yoked exclusively to the six-cylinder as a gas-saver.

A Trio Emerges

By the early '80s around the M-body cars had assumed a bigger role in the Chrysler family. Styling had been revised to provide a more stern, luxury look, and although they remained somewhat smaller than full-size options from General Motors (the Chevrolet Caprice) and Ford (the Crown Victoria), they were big enough to pull family duty.

1980 Dodge Diplomat line-up

Cash-strapped Chrysler's early-decade investment in front-wheel drive meant cutting back on M-body options. By the end of 1982 the wagon and coupe versions of the Diplomat were out of the picture, the Plymouth Caravelle had been imported from Canada to be sold as the Gran Fury, and the Chrysler Fifth Avenue (originally sold as the New Yorker Fifth Avenue) had replaced the LeBaron.

Plymouth Gran Fury front view

Chrysler only began selling the Diplomat (and eventually the Gran Fury) to police fleets in 1981 (instead offering its R-body cars to close out the previous decade). Once the M-body began to reach a wider audience, police pack cars would come close to half of total Gran Fury production for Plymouth, and it added a 4-barrel carburetor to the vehicle's (now-standard) 318.

Dodge Diplomat police car

In 1985 a higher compression version of the motor arrived, and thanks to an aggressive camshaft the civilian version was able to produce 265 lb-ft of torque to go with its 140 hp rating (or 175 hp and 250 lb-ft of twist for police pack versions).

Dodge Diplomat and Plymouth Volare

Taxi operators would also gobble up the M-bodies. By 1989, the final year of production, the vast majority of Dodge and Plymouth versions of the sedan were being purchased by fleets. Surprisingly, Chrysler's Fifth Avenue would outsell its lesser siblings, thanks largely to modest pricing that made it seem like a 'cheap' way to get into what was at the time perceived to be a premium brand.

Cheap And Simple Project Cars

A big part of why fleet buyers loved the M-body is also the reason why it makes an intriguing option for car collectors today: its very simple design is both durable and inexpensive to repair.

Chrysler Fifth Avenue in black

All versions of the Diplomat, Gran Fury, and Fifth Avenue come with leaf springs at the rear matched with Chrysler's torsion bar front suspension and paired with a front sway bar. This gives the cars only modest handling capabilities compared to a modern vehicle, but at the time it was relatively resistant to body roll (making it easy to toss around corners in the scores of cop movies it starred in). This basic suspension setup is combined with big 11-inch front brake disks and rear drums.

Dodge Diplomat hood ornament

Both of its LA engines are very well supported from an aftermarket perspective, and continued well past the cars' 1989 cut-off dates to continue to pull duty under the hood of Dodge' Ram and Dakota pickup trucks. Headers, intake, heads, and the standard list of V8 hot rodding tricks work on both the 318 and the 360, with Magnum engine swaps (complete with fuel injection) also a possibility.

Plymouth Gran Fury police pack

The M-body continues to be overlooked in a market that has instead focused on its Ford and Chevrolet competitors. The Diplomat, Gran Fury, and even the plush Fifth Avenue offer the chance to drive something different that captures the last of Chrysler's Rad-era rear-wheel drive fun.

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