The 956 features a chassis made of an aluminium monocoque, a first for the company, helping to allow the car to meet the weight minimum in Group C. The engine is the same as the one used in the Porsche 936, the Type-935 2.65 L turbocharged Flat-6, producing approximately . A new 5-speed gearbox was also designed for the 956. High downforce aerodynamics allowed the car to be capable of reaching 252mph (+400km/h) on the Mulsanne Straight at the 24 Hours of Le Mans.
An improved chassis with better fuel efficiency from a Bosch Motronic electric system was developed for 1984, being termed the 956B. In total, twenty-eight 956s would be built by Porsche from 1982 to 1984, with an unofficial 29th chassis built from spare parts by Richard Lloyd Racing.
In 1983, 956 chassis #107 was used by Porsche as a testbed for their P01 Formula One engine, later badged as TAG and used by McLaren. The car was able to test some of the characteristics of a Formula One car in order to develop the engine.
The 956 would be officially replaced by the Porsche 962 in 1985, an evolution in the 956's design.
The 956 made its debut at the Silverstone 6 Hour race, the second round of the World Championship for Makes with Jacky Ickx and Derek Bell driving for the factory. After missing the following round at the 1000 km Nürburgring for developmental reasons, the Ickx/Bell unit reappeared at the 24 Hours of Le Mans. They led the race for the entire 24 hours, eventually taking the overall win - their third win together. As they had already won in 1981 with a Porsche 936 that had used an early version of the 956 engine, their car had start number 1. The two other factory 956 followed them, so the three factory Porsches finished 1-2-3 in the order of their starting numbers.
Boosted by this success, Porsche sold customer versions of the 956 to privateer teams such as Joest Racing, Obermaier Racing, John Fitzpatrick Racing, Richard Lloyd Racing, Kremer Racing and Brun Motorsport who raced them independently of the factory.
The overall all-time lap record for the demanding 20 km Nürburgring-Nordschleife circuit in the Eifel Mountains has been achieved during the qualifying session for the 1983 1000 km Nürburgring, by Stefan Bellof, who drove his 956 around in 6 minutes 11.13 seconds, at an amazing average speed (considering the difficulty of the track layout) of . The race lap record is held by the same Bellof, during the 1983 1000 km Nürburgring, the lap being clocked at 6:25.91.