The Chrysler Sigma is a version of the Mitsubishi Galant automobile that was built by Chrysler Australia in Adelaide, South Australia from 1977. When Mitsubishi Motors Australia (MMAL) took over Chrysler Australia's manufacturing facilities in 1980, they renamed the vehicle the Mitsubishi Sigma. The range was progressively discontinued and replaced by the Mitsubishi Magna, starting with the sedan in 1985 and the wagon in 1987.
First generation
GE (1977–1980)
Chrysler launched the GE series Sigma in October 1977 to replace the outgoing GD Galant. Assembly occurred at the Tonsley Park, Adelaide plant.
The GE series Sigma was the first to introduce the Australian market to the Astron engine range. The 1.6-litre Saturn engine with four-speed manual transmission was also available in the base model, badged Sigma Galant. The Saturn engine was good for of power and of torque. The mid-range model, the Sigma GL, came standard with the 1.85-litre Astron and four-speed manual,
Outputs for the 2.0-litre were and .
Sigma SE offered equipment including five-position, reclining rear seats.
From launch, Chrysler also offered a "Sportspack" option for the GL 2.0-litre.
In March 1978, a Japanese-made, two-door coupé version called the "Sigma Scorpion" was released—based on the Mitsubishi Galant Lambda.
On 1 November 1979, Chrysler announced and commenced sales of the enlarged, 2.6-litre Astron engined Sigma GL and SE. At the same time, the 1.85-litre engine was dropped. Paired only with the automatic gearbox, 2.6-litre was believed to be the biggest four-cylinder engine sold internationally at the time. 14-inch cast alloy wheels were also made available as a further option for the 2.6. Its large displacement made it competitive with six-cylinder rivals.
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File:1978 Chrysler Sigma (GE) GL Sportspack sedan (17299461025).jpg | Chrysler Sigma (GE) GL Sportspack sedan
File:1977-1980 Chrysler Sigma (GE) SE sedan (16987763925).jpg | Chrysler Sigma (GE) SE 2.0 sedan
File:1979-1980 Chrysler Sigma (GE) SE sedan (2008-12-19).jpg | Chrysler Sigma (GE) SE 2.6 sedan
File:1978 Chrysler Sigma (GE) GL Sportspack sedan (17299473875).jpg | Interior, Chrysler Sigma (GE) GL Sportspack sedan
File:Chrysler Sigma SE Wagon (GE).jpg|Chrysler Sigma SE Wagon (GE)
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GH (1980–1982)
On 28 April 1980, Chrysler unveiled the GH Sigma in Brisbane. Then on 30 April, Mitsubishi Corporation and Mitsubishi Motors jointly acquired Chrysler's remaining 65 percent share of Chrysler Australia (bringing the dual Mitsubishi ownership to 98.9 percent). On 1 October 1980, the GH range was rebadged from Chrysler Sigma to Mitsubishi Sigma, due to the renaming of Chrysler Australia to Mitsubishi Motors Australia (MMAL) following the buy-out.
Released to the market on 12 May, the GH series saw a considerable facelift on both front and rear ends. While it was only introduced to Australia in 1980, the facelift actually appeared on the Japanese home market Galant models and on New Zealand assembled Mitsubishi Sigma models in 1979.
The mechanical layout was as before except for addition of a five-speed manual for the 2.6-litre model (with automatic exiled to the options list). The base model was now simply called "Sigma" instead of "Sigma Galant".
A GLX model was placed between GL and SE level and was advertised as a "sports pack". A limited run of 1,016 "Peter Wherrett" editions of the GLX were built (option A05), named after Australian motoring journalist Peter Wherrett who was given the task of improving the handling of the Sigma by MMAL after complaining about it. The improvements included 15-inch Globe "Montego" alloy wheels fitted with Pirelli P6 tyres, Recaro seats, Momo steering wheel, Sonic extractors, as well as lowered coil springs and Bilstein shock absorbers.
Mitsubishi released a limited edition, GL-based Sigma Satellite in c. April 1981, adding two-tone paint (available in three combinations), unique hubcaps, a soft grip sports steering wheel, cloth upholstery, full tinted glass including laminated windscreen. In September 1981, in partnership with turbocharger specialists Normalair-Garrett, Mitsubishi produced a limited run of 500 Sigma Turbos, the first Australian-built turbocharged production car. The forced-induction 2.0-litre Astron powerplant produced and . Mitsubishi discontinued the GH series in February 1982.
Second generation
GJ (1982–1984)
thumb|Mitsubishi Sigma (GJ) GL Satellite sedan
thumb|Mitsubishi Sigma (GJ) SE station wagon
The redesigned GJ Sigma was released in March 1982, based on the 1980 Japanese domestic market Mitsubishi Galant. While a complete redevelopment was done for the sedan models, the wagon models in fact were new only from the firewall forward—the rest of the bodyshell was still GH based. Engine and transmission offerings remained as before, but received power and torque boosts; the 2.0-litre now produced and and the 2.6-litre and .
In February 1983, Mitsubishi launched a special edition Sigma GL Satellite. Priced $1,000 below the GL luxury level, the Satellite was built in sedan and wagon versions, with air conditioning, five-speed manual or automatic transmission all as options. However, two-tone paintwork, a laminated windscreen, AM/FM radio, adjustable steering column, intermittent windscreen wipers and a heated rear window were fitted as standard equipment.
thumb|left|Mitsubishi Sigma (GJ) GL sedan
A sporting model, the Sigma GSR, was also released with either 2.0 or 2.6-litre engines offered with either automatic or manual transmissions. Features included alloy wheels, four-wheel disc brakes, a sports steering wheel and blackouts, particularly on the window frames and doorhandles.
June 1983 saw the entry-level Sigma rebadged as the Sigma XL, to coincide with the trim level designations on MMAL's small car, the Colt.
October 1983 saw the release of the luxurious, Sigma Super Saloon. Produced as a limited edition of 500 cars and placed above the SE trim level from which it derives, it came only with the 2.6-litre in either five-speed manual or three-speed automatic. The Super Saloon featured two-tone metallic paint and crushed velour upholstery for the interior. The GK Super Saloon generally followed the GJ's structure, although changes included new corduroy trim and stereo system with Compact Cassette facility, AM/FM scan tuning, and digital display.
GN (1985–1987)
thumb|Mitsubishi Sigma (GN) GL wagon
thumb|right|Mitsubishi Sigma (GN) GL wagon
Released in July 1985, the GN was an update, but also a rationalization of the previous Sigma range due to only being offered in GL trim. The range was rationalized due to the April 1985 release of the Mitsubishi Magna front-wheel drive range, which was developed eventually to replace the Sigma in Australia.
thumb|left|Mitsubishi Sigma (GN) GL sedan
The GN range had a number of external trim changes over its predecessors, notably a black trim line around the base of the body, and the deletion of the wrap-round chrome strip seen on the previous model. The grille was remodelled, resembling the SE grille of the previous model, and new hubcaps were used with alloy wheels from the previous SE models optional. The largest change however, concerned the wagon models. To freshen the model before the impending release of the Magna wagon (which was being developed at that time, for a 1987 release), a new higher roof (dubbed "high roof") was developed for the car, which helped to improve the car's overall cabin space. It gave the wagon a unique appearance from its predecessors, particularly as it incorporated a roof-mounted spoiler.
Engine-wise, the GN Sigma was offered either with the Astron 2.0-litre ( at 5600 rpm and at 2400 rpm) or the Astron II 2.6-litre ( at 5200 rpm and at 2400 rpm) units. The Astron II had a few changes over the previous models, notably a newly designed head with hydraulic tappets (replacing the manual tappets in previous Astrons) and flat-top pistons. The oil pressure switch was now located at the rear of the cylinder block. In December 1985, the 2.0-litre versions were dropped, as Mitsubishi did not believe it warranted the conversion to unleaded fuel. Unleaded was introduced in Australia in January 1986.
Mitsubishi launched GL Satellite limited editions of the GN series in c. October 1986, adding air conditioning, unique striping, headlamp protectors, front and rear mudflaps, tilt adjustable steering column, remote control tailgate (for wagons) and side mirrors.
The "high roof" Sigma wagon was an export model for MMAL. During 1986–1987 station wagons were shipped to New Zealand, due to that market's demand for wagon models. Although they were of a previous generation to the front-wheel drive Mitsubishi Sigma sedan (which was similar, but of a narrower bodyshell to the Magna, and fitted with smaller engines) range being sold in New Zealand, they proved popular, particularly with fleets.
This final generation of the Sigma ceased production in early 1987, due to the release of the Magna wagon models, completing the overall Magna range.