The General Motors Sigma platform is a mid-size automobile platform used by General Motors from the 2003 to 2015 model years. Exclusive to the

Cadillac Cadillac Motor Car Division, or simply Cadillac (), is the luxury vehicle division (business), division of the American automobile manufacturer General Motors (GM). Its major markets are the United States, Canada and China; Cadillac models are ...

division, Sigma was the successor to the Opel-designed V platform. Initially developed for

executive cars Executive car is a British term for a large car, and is considered equivalent to the European E-segment and American full-size car, full-size classifications. Executive cars are larger than compact executive cars (and the non-luxury equivalent m ...

, the architecture was expanded for larger model lines, sports sedans, and multiple body styles. Two generations of the Sigma platform were developed by GM for worldwide markets. The architecture was discontinued for the 2016 in favor of the GM Alpha platform, itself utilized nearly exclusively by Cadillac.

Sigma I

The first Cadillac-exclusive platform since the D-body chassis, Sigma debuted in early 2002 for the 2003 model year underpinning the

Cadillac CTS The Cadillac CTS is a luxury car, manufactured and marketed by General Motors from 2003 until 2019 across three generations. Initially available as a 4-door sedan using the GM Sigma platform, GM offered the second generation CTS in 4-door ...

, replacing the Cadillac Catera. Slightly larger than its V-body predecessor, the rear-wheel drive Sigma architecture was developed to accommodate all-wheel drive and extended-wheelbase variants. For 2004, the Cadillac STS was introduced on the Sigma platform, replacing the Cadillac Seville. Sharing its wheelbase with the STS, the Cadillac SRX was introduced for 2005 as the second Cadillac SUV, slotted below the Escalade in size. The Sigma platform uses four-wheel independent suspension with front control arms and a rear multi-link configuration. Initially powered by variants of the

General Motors 54° V6 engine General Motors' Opel subsidiary in Europe designed a compact V6 engine with an unusual 54° vee angle. It was an iron block/aluminum head DOHC design with four valves per cylinder. All 54° engines were assembled at Ellesmere Port in England. His ...

family, the platform introduced additional engines, including the High Feature V6 and Northstar V8. Exclusive to the high-performance CTS-V, the Sigma platform was developed to accommodate the 5.7L LS6 and 6.0L LS2 V8 engines of the Chevrolet Corvette. Outside of the CTS (which offered a standard 5-speed manual and a 6-speed manual for the CTS-V), all Sigma vehicles utilized GM 5-speed 5L40/5L50 automatic transmissions. The Sigma architecture marked several firsts, as the CTS was the first Cadillac since the 1986 Cadillac Cimarron to be offered with a manual transmission. The 2004 STS became the first rear-wheel drive Cadillac sedan to offer the Northstar engine (originally developed for front-wheel drive applications). The China-market Cadillac SLS became the first non-limousine Cadillac sedan line introduced as a extended-wheelbase variant. Vehicles based on this platform: * 2003–2007

* 2004–2009 Cadillac SRX * 2005–2011 Cadillac STS * 2007–2013 Cadillac SLS (China)

Sigma II

GM debuted Sigma II with the 2008 Cadillac CTS. While sharing the previous 113.4-inch wheelbase, the platform was longer and wider than the previous generation. Remaining exclusive to the Cadillac division, the design adopted a greater degree of parts sharing with the Australian-designed Zeta platform. The High Feature engines were carried over to Sigma II, with the CTS-V receiving a supercharged LSA V8 (a variant of the Corvette ZR1 engine). Sigma II became exclusive to the CTS, as the SRX was downsized for 2010, adopting the Theta Premium architecture and the STS was retired after 2011 (the SLS, 2013) with no direct successor. For 2011,

coupé A coupe or coupé (, ) is a passenger car with a sloping or truncated rear roofline and typically with two doors. The term ''coupé'' was first applied to horse-drawn carriages for two passengers without rear-facing seats. It comes from the Fr ...

and

station wagon A station wagon (American English, US, also wagon) or estate car (British English, UK, also estate) is an automotive Car body style, body-style variant of a Sedan (automobile), sedan with its roof extended rearward over a shared passenger/cargo ...

variants were introduced on the Sigma II platform (marking the first Cadillac coupe with a rear seat since the 2002 Eldorado) Applications: * 2008–2013

* 2009–2015 Cadillac CTS-V

References

{{General Motors platforms

Sigma Sigma ( ; uppercase Σ, lowercase σ, lowercase in word-final position ς; ) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 200. In general mathematics, uppercase Σ is used as an operator ...