For two brief shining moments, 1971 and '74, Plymouth again finished its traditional third in industry production. But after that, it never ran higher than fourth. By decade's end Plymouth had sunk to ninth, even though 1979 was a very healthy Detroit year. By the early '80s, the make was all but invisible.
Several factors contributed to this sorry decline: more wrong products at wrong times, indifferent workmanship even on the few models that were well timed, dwindling public confidence in Chrysler Corporation generally, and decreased styling distinction with related Dodges.
Plymouth also suffered from a growing dullness that stemmed from the '60s consolidation of Chrysler's five divisions into two (Dodge and Chrysler-Plymouth). Because this eliminated the need to put all nameplates on all major platforms, glamour assignments like Cordoba went to Chrysler while Dodge increasingly got sportier models all to itself. By 1978, Plymouth was back to peddling basic family transportation -- just as it had started out doing 50 years before.
Yet few could have foreseen this diminished role in 1970, when Plymouth countered Ford and Chevy with five separate car lines spanning 44 individual models and about 70 basic variations (counting trim levels and engines).
Valiant, the lone survivor of the original Big Three compacts, dominated its market right on through swan-song '76. A key factor was the Duster coupe, which chalked up well over a quarter-million sales for 1974 alone. It was conventional but cute and well-engineered, and at least as well-built as comparable GM and Ford products.
Plymouth kept Duster desirable with a stream of extra-cost packages. The 1971-74 "Twister" option included matte-black hood, Duster 340-type black grille, bodyside tape stripes, and Rallye wheels. The Gold Duster continued through 1975 with a color-keyed pebble-grain vinyl roof. The "Space Duster" of 1973-74 was Plymouth's equivalent of Dodge's Dart Sport "Convertriple," with a wagon-style fold-down rear seatback that gave a 6-1/2-foot-long carpeted cargo deck. (Shades of the original Barracuda.)
Even at the end of the line there was a special "Silver Duster" (a handsome combination of silver, red, and black) as well as a "Feather Duster." The latter, a reply to Ford's "MPG" models, had an economy-tuned 225 Slant Six with aluminum intake manifold, and aluminum instead of steel inner panels for hood and decklid. With a manual-overdrive gearbox, which had an aluminum case, the Feather Duster was surprisingly frugal; a prudent driver could nurse one up to 30 mpg.
Further bolstering the Valiant line were the performance-oriented V-8 Duster 340 (through '73) and 360 (1974-75); the 1974-76 Brougham luxury option for sedans and two-door hardtops, offering opulence not usually found in compacts; and the Scamp hardtop, which was new for 1971. Altogether, Valiant and Dodge's similar Dart were impressive sellers right to the end. In some years Valiant gave Chrysler the compact lead over Ford and Chevy.
Unveiled for mid-'76 was Volare, a more upscale Plymouth compact that replaced Valiant entirely the following year. Though only a bit larger outside, Volare (and its Dodge Aspen cousin) had been designed for maximum interior space, which was quite good for the day. Workmanship, however, was anything but good.
Still, this very real problem didn't harm sales right away, mainly because it didn't surface for a few years. Trim levels comprised base, mid-range Custom, and high-line Premier; the last offering unexpected luxury for around $4500. Volare also came as a five-door wagon in addition to the expected coupe and sedan -- Plymouth's first compact wagon since 1966.
The Volare was right on target, racking up almost 400,000 sales for '77. Most examples had a 225 Slant Six or 318 V-8, both able veterans of some two decades. Though no trend-setter, Volare appealed mainly for its restrained styling and a decent performance/economy compromise.
Compacts were Plymouth's only real success in the '70s; its intermediates and full-size cars fared poorly. So, too, did the Barracuda, which was of no significance in the steadily declining ponycar market.
The all-new 1970 design was warmed over for '71, gaining quad headlamps and a none-too-pretty Vee'd grille with vertical slats. A low-priced pillared hardtop replaced the convertible Gran Coupe and promptly took the lion's share of drastically reduced sales.
Convertibles and big-block power were scrubbed for '72, leaving standard and 'Cuda V-8 coupes. These carried on for two more seasons before Plymouth gave up. Low production has thrust 'Cudas and Gran Coupes into the collector limelight -- especially convertibles. The '71 droptop 'Cuda saw just 374 copies, and the standard convertible was almost as rare at 1014.
Midsize Plymouths consolidated under the Satellite name for 1971 and were completely revamped, shedding their relatively square 1968-70 look for more radically sculptured sheetmetal and large loop bumper/grilles.
In line with a Detroit trend, coupes rode a shorter wheelbase than sedans and wagons (115 vs. 117 inches). Convertibles vanished here too, but Road Runner and GTX were still around, and there was a smart new sports-luxury hardtop called Sebring Plus.
Unfortunately, these Plymouths suffered the same fate as most '70s intermediates, becoming ever-more ponderous, thirsty, and ugly. The GTX was dumped after '71 for lack of sales, and the Road Runner, still ostensibly a separate model, wasn't nearly as fast on its feet as before.
An attempt to regroup for 1975 brought the "small Fury," basically the existing platform with squared-up outer sheetmetal and a new name, but sales continued to languish. The last of these cars rolled out the door in 1978.