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Overview - The below outlines all of GM's North American and "global" architectures. In the GM world a platform is designated "global" when it is built in multiple countries. Over the next few years GM is expected to consolidate the majority of their vehicles to three core platforms: Gamma, Delta, and Epsilon.


Last Updated: July 29, 2013

Gamma - Global Small Vehicle


Size Class: Subcompact (A and B-class)

Format: Body-frame integral

Drivetrain: Front-wheel drive

Suspension: Strut-type front, with semi-independent torsion beam rear (compound crank rear in lower end applications)


The Gamma platform originates from when GM and Italian automaker Fiat were teamed up. The platform first underpinned the Opel Corsa C in the year 2000, as well as some Fiat models. Over time GM began to use the platform more and has since evolved it with the second iteration of the platform, Gamma II or "Global Small Vehicle."

 

While the original Gamma was developed with Opel, Gamma II is under the leadership of GM Korea (formally GM Daeweoo). Gamma II first launched with the 2010 Chevrolet Spark, and has since spawned the Chevrolet Sonic (Aveo), Opel Corsa, Opel Adam, and several other subcompact vehicles. GM eventually wants all small (A and B-class) vehicles to be on the Gamma II architecture.

Delta - Global Compact Vehicle


Size Class: Compact (C-class)

Format: Body-frame integral

Drivetrain: Front-wheel drive

Suspension: Strut-type front, with semi-independent torsion beam rear (higher end cars have a Watt's Link rear)

 

Delta traces its routes to GM's European Opel subsidiary. Opel developed the chassis as an effort to replace several of the older front-wheel drive architectures GM was using around the globe at the time. During development, insiders specifically stated that the VW Jetta was the benchmark for the development of the chassis, specifically for the Chevrolet Cobalt. Delta was first launched with the Saturn Ion, followed by the Opel Astra and Chevrolet Cobalt.

The Delta architecture is now on it's second generation, referred to as Delta II or "Global Compact Vehicle." Like the original, Delta II has largely been developed by Opel, however all of GM's engineering centers have input on it. The platform also serves as the basis for the Chevrolet Volt and Cadillac ELR extended range electric vehicles.


Going forward Delta II will morph into underpinning a line of compact crossover vehicles, `including the next-generation Chevrolet Equinox and GMC Terrain. The idea is that Delta II will ultimately replace today's Theta and TE crossover chassis.

Epsilon - Global Midsize Vehicle


Size Class: Midsize/Large (D and E-class)

Format: Body-frame integral

Drivetrain: Front-wheel drive or all-wheel drive

Suspension: Strut-type front with multi-link independent rear (typical)

 

Like Delta, Epsilon was originally developed by Opel in Europe. The Epsilon chassis first debuted in 2003 on the Opel Vectra. Since it's original launch it has evolved greatly to include multiple wheelbases, multiple suspension setups and has spawned a host of vehicle world-wide.

 

The second generation of Epsilon launched in 2008 with the Opel Insignia. Epsilon II served as a means of consolidating GM's midsize cars globally to one architecture (the original Epsilon was very fragmented). Since then a long wheelbase version of the chassis underpins cars such as the Buick LaCrosse and Chevrolet Impala, while the Cadillac XTS rides upon a version of Epsilon referred to as "Premium Epsilon." The name change is due to the extensive changes to the XTS' suspension versus the other Epsilon cars.

Zeta


Size Class: Midsize/Large (D and E-Class)

Format: Body-frame integral

Drivetrain: Rear-wheel drive

Suspension: Strut-type front with multi-link independent rear

 

The Zeta chassis has a long, storied past. It was derived by Holden back in 1999 after GM North America took development of the Sigma chassis away from them to use at Cadillac. Zeta does not where a "global" title because it is an architecture that is primarily assembled in one country: Australia. Yes, the Camaro is build in Canada, however it has significant modifications from Holden's Zeta. It's almost a one-off of the chassis.

 

There are two primary wheelbases of Zeta; a short one that the Holden Commodore rides on, and a longer one that the Holden Statesman rides on. For the long version of the Zeta story, click here.

Alpha


Size Class: Compact/Midsize (C and D-Class)

Format: Body-frame integral

Drivetrain: Rear-wheel drive or all-wheel drive

Suspension: Strut-type front (or Magnetic Ride Control monotubes) with five-link independent rear (or Magnetic Ride Control monotubes)

 

After realizing that the larger Sigma rear-wheel drive chassis could not be scaled down to compete in the compact luxury segment, GM began developing what is now Alpha. The Alpha chassis is a ground-up new chassis that is, if anything, incredibly simple in design. At it's core, Alpha is a lightweight chassis with 50/50 weight distribution. All Alpha cars utilize a ZF steering system and other high end components that allow Alpha cars to run in the same pack as the best from Germany

 

Once the 2014 Cadillac CTS launches later this year, there will be two wheelbases of Alpha. The long wheelbase version of the Alpha is sometimes referred to as Alpha+.

Sigma


Size Class: Midsize (D and E-Class)

Format: Body-frame integral

Drivetrain: Rear-wheel drive or all-wheel drive

Suspension: Four-wheel independent

 

Sigma originates from 1998, back when Holden began developing it. After the GM mothership latched on to Holden's work, the 2003 Cadillac CTS was the first car to launch on Sigma. The second iteration of the chassis launched in 2008 with the second gernation CTS. Sigma II is slightly longer and wider than it's predecessor, however it is more flexible than the original Sigma. Sigma II will be phased out once the new CTS launches later this year.

Y-Body


Size Class: Performance Coupe

Format: Hydroformed aluminum frame with aluminum and magnesium structural components

Drivetrain: Rear-wheel drive

Suspension: Double wishbone front and double wishbone rear, monotube shock absorbers all around

 

Y-Body has been the defacto name for the Corvette chassis since 1984. It is unique not only in that it underpins a car that can run with the world's exotics, but also by design. The chassis uses a central-tunnel design that helps maintain a 50/50 weight distribution by placing a torque tube between the engine and transmission. The tube allows the heavy transmission to be mounted toward the rear of the car, thus balancing the weight out from the engine up front.

 

The defunct Kappa platform used many of the design traits of Y-Body.

Truck Platforms

Theta


Size Class: Compact and Midsize Crossovers

Format: Body-frame integral

Drivetrain: Front-wheel drive or all-wheel drive

Suspension: Four-wheel independent

 

Theta launched in 2002 with the Saturn Vue. Since then several iterations of the Theta chassis have come to fruition - in fact, Theta is actually fairly fragmented compared to the latest versions of GM's global architectures. There are two dominate versions that are still in production: a short wheelbase version that the Opel Antara and Chevrolet Captiva utilize, and a long wheelbase version that the Chevrolet Equinox and GMC Terrain utilize.

 

Over time it is expected that the Theta crossovers will be replaced by the Delta II platform as GM consolidates global platforms.

Theta Premium / TE


Size Class: Midsize Crossovers

Format: Body-frame integral

Drivetrain: Front-wheel drive or all-wheel drive

Suspension: Four-wheel independent

 

This particular chassis wears several names. Interally and externally it is universally referred to as Theta Premium and TE, TE standing for "Theta Epsilon." The TE name comes from the alleged fact that this version of Theta encompasses several commonalities with both the Theta and Epsilon II platforms. It's ties to Epsilon also allow it to be slightly larger than the other versions of Theta.

 

TE was developed to underpin the Cadillac SRX and Saab 9-4x. While the Saab no longer exists, the SRX remains on TE today. Though we hear that the SRX will eventually move to a new platform that has more commonality with the Epsilon architecture.

Lambda


Size Class: Midsize/Large Crossovers

Format: Body-frame integral

Drivetrain: Front-wheel drive or all-wheel drive

Suspension: Coil-over strut w/ stabilizer bar in front, linked H-arm independent rear

 

Lambda is largely derived from the Epsilon platform, however commonality between the two is apparently minimal. GM is expected to phase out the Lambda platform and replace it with a new one that shares more with Epsilon.

 

Sources have always indicated that Lambda has a vast amount of constraints due to it's uniqueness from the rest of GM's global architectures. For example, Lambda products still use the older LLT 3.6L V-6, while every other product has migrated to the more powerful LFX.

K2XX


Size Class: Full-size trucks and SUVs

Format: Body on frame

Drivetrain: Rear-wheel drive or four-wheel drive

Suspension: Coil-over shock front, solid axle with two-stage multileaf springs

 

K2XX is the successor to GMT-900, and shares much with it. The overall construction of K2XX is very similar to the 900, however K2XX is slightly more capable. GM has added things such as hydralic cab mounts on certain truck configurations to give the trucks a smoother ride without compromising ability.

GMT-900

Things to know-
  • A new, fully boxed frame that is significantly stronger and stiffer with hydro formed front and rear bay sections.
  • Wider front and rear tracks – approximately 3 inches (76.2 mm) in front and 1 inch (25.4 mm) in rear – enable increased stability, a well as a smoother, more controlled ride.
  • New coil-over-shock front suspension delivers linear, responsive ride and handling characteristics.
  • Highly refined five-link rear suspension (with variable-rate springs) delivers damped, isolated road feel and supports a variety of load-carrying capabilities.
  • Use of monotube Autoride shock absorbers for more controlled, real-time damping capability.
  • New rack-and-pinion steering system delivers precise, responsive steering and contributes to the vehicles' "drive small" feel.
  • All-new four-wheel disc brake system larger vented discs, stiffer calipers, more robust apply system and standard next-generation Bosch ABS system provides shorter stopping distances, better pedal feel and quicker brake response.
  • Larger-diameter standard and available wheels and tires, including segment-largest, 22-inch designs available on Cadillac Escalade.
  • Standard StabiliTrak electronic stability control with first-time GM application of rollover mitigation – a software algorithm technology that uses system sensors to proactively predict vehicle "tip-up" and applies appropriate brake forces to prevent rollovers
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