Mopar Rear Drive Unit Bodies

Mopar performance enthusiasts are sometimes myopic. With "LA", "RB", and Hemi engines to talk about, it is easy to overlook the engineering advancements of the cars that carried these great engines. In this article, we will take a look at the history of Chryslers rear wheel drive unit bodies and also cover which cars were built on which chassis.

History

In 1960, Chrysler converted all models except Imperial from body on frame construction to unitized construction. By combining the body and frame into one structure, unitized, or unit body, construction increases strength and reduces weight. While it can be argued that the Airflow sedans of the 1930s were the first use of unit bodies by Chrysler, the 1960 bodies were a substantial technical advance.

The new Chrysler chassis was notable for reasons other than its unique construction. There were now three distinct sizes of vehicle available. The largest or standard size body was used by Chrysler, Dodge, and Desoto. The intermediate body was used by Dodge and Plymouth. The compact body was exclusive to Plymouth in 1960 and expanded to Dodge in 1961.

The first generation unit bodies maintained Chrysler's now famous longitudinal torsion bar suspension. Introduced in 1957, this suspension stayed in production until 1981. In the mid 1970's, Chrysler introduced a new unit body that used transverse torsion bars. This suspension stayed in production until 1989 when Chrysler temporarily ended production of rear wheel drive passenger cars.

Alphabet Soup

Chrysler grouped its chassis into platforms. These platforms were given a code to identify them. Cars built on the same platform have many parts that are interchangeable.

The following section gives a model breakdown by platform. The chassis that use longitudinal torsion bars and the chassis that use transverse torsion bars are grouped together.

Logitudinal Torsion Bar Chassis

The first unit bodies developed by Chrysler made good use of the parallel longitudinal torsion bar front suspension that was introduced in 1957. While it was refined in several ways, the basic design continued in production until 1981. In fact, a variation is currently under the front of four wheel drive Dakotas and Durangos.

A Body

The smallest of Chrysler's unit bodies was introduced with a new slant six engine. The initial styling was considered European and was reviewed better than it sold. A re-skin in 1963 brought the cars closer to the mainstream. A 273 cubic inch V8 was available in 1964. This new LA engine was a tight fit in the A body and in the performance race of the sixties, even compacts were expected to carry big blocks. The chassis was widened in a 1967 redesign that would carry over until the chassis was retired in 1976.

B Body

The intermediate class chassis was a new idea in 1960, but eventually became the mainstay of the Dodge and Plymouth line up. The chassis was redesigned for a slight downsize in 1962. This proved unpopular and the chassis was lengthened in 1963. There were minor redesigns in '66 and '68. A major redesign in 1971 included many of the features of the year old E body. In '73 the chassis had a set of refinements to increase passenger isolation.

E Body

The E body was Chrysler's entry into the sporty (pony) car market. This chassis was based on the B body which caused the cars to be heavier than competing cars in this class. Unfortunately, the E bodies were late to market and their death warrant was signed as the first cars rolled off of the assembly line in 1970.

C Body

The full size chassis represented the standard sized cars when it was released in 1960. The C body was little more than a stretched B body until 1965 when a new chassis was released. The new chassis featured a bolt on front sub-frame. Minor redesigns took place in 1969 and 1972.

R Body

The R body was the last incarnation of the longitudinal torsion bar chassis. This chassis was used for premium luxury cars.

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Transverse Torsion Bar Chassis

Chrysler introduced the transverse torsion bar chassis in 1977 in the compact Aspen and Volare. The use of transverse torsion bars was influenced by the desire to increase the isolation of occupants from ride harshness and the need to simplify the construction process of the chassis.

The transverse torsion bars were a compromise that cause complications when using this suspension in a performance application. Despite the promise of simpler construction, models that used this suspension suffered quality problems. Most of these problems were worked out by the mid '80s but by then Chrysler was on an all front wheel drive path.

F Body

The F body replaced the A body as the basis of Chrysler compacts. This chassis introduced transverse torsion bars.

M Body

The M body was a larger version of the f body. This chassis was used in the last mainstream rear wheel drive Chrysler products.

J Body '80-'83

The J body was the basis for Chryslers entry into the hot personal luxury car segment that emerged in the mid '70s. These cars were produced as the market was winding down.

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