Sport Sedan, Sport Coupe, Custom Coupe, convertible and Kingswood wagon, and optional on the sedan). Optional engines included the 255-horsepower 400 cubic-inch Turbo Fire V-8 (the standard Caprice and Kingswood Estate engine), 300-horsepower 400 cubic-inch Turbo Jet V8 and 365-horsepower 454 cubic-inch V-8. Early in the model year, all Impalas came standard with three-speed column shift manual transmissions and manual steering as standard equipment, with power steering and one of two automatic transmissions optional. During the first months of the model year, the three-speed Turbo-Hydramatic automatic transmission was optional with all engines while the two-speed Powerglide could be ordered with the 250 6 or 350 V-8s. At mid-year the Turbo-Hydramatic and variable-ratio power steering became standard equipment on all V-8 powered full-sized Chevrolets. Station wagons featured a 'clamshell' design where the rear power-operated glass slid up into the roof as the tailgate (manually or with power assist), dropped below the load floor. The power tailgate, the first of its kind, ultimately supplanted the manual tailgate which required marked effort to lift from storage. This design was shared with other full-sized GM wagons from Pontiac, Oldsmobile and Buick. Subsequent generations reverted to the door-gate style for its full-size wagons. As expected, 1971 Impala production was well below 1970 totals due to the 67-day corporate wide strike at General Motors that began in September, 1970 after initial 1971-model production began and would not end until November. Impala production ended up at 427,000 units including 2,300 with six-cylinder engines and 425,400 with V8 with other series production totals including Caprice, 91,300; Biscayne, 37,600; Bel Air, 20,000; and station wagons (all series), 91,300. 1972 The 1972 Impala introduced a lower height grille which extended below the bumper and revised taillights now set in the bumper. 1972 saw the last Impala convertible, the following year moving to the top-of-the-line Caprice Classic. The Impala ragtop sold 6,456 units, placing fourth with just under 9% of the market, right behind the Corvette 6,508, and the Cutlass Supreme's 11,571, while remaining ahead of the Mustang's 6,401. Total Impala production for 1972 ended up at 597,500 units and other series totals included Caprice, 178,500; Biscayne (in its final year), 20,500; Bel Air, 41,900; and station wagons, 171,700. The 250-cubic-inch six-cylinder engine was offered in Impala four-door sedans and sport coupes along with a three-speed manual transmission and manual steering at the very beginning of the model year with 1,500