GEC Traction (GECT) was formed in 1972 as part of the GEC Power Engineering Group following earlier amalgamations of the traction divisions of the General Electric Company (GEC), the English Electric Company (EE) and Associated Electrical Industries (AEI). A wholly owned subsidiary company of GEC, the company had offices and works, located at Trafford Park in Manchester, at Strand Road in Preston, and at Attercliffe Common, Sheffield. The headquarters of GEC Traction was Trafford Park, Manchester (previously the headquarters of English Electric-AEI Traction) with design of rotating machines at Preston and Sheffield, and manufacturing activities for control equipment at Manchester and Preston. GEC Traction designed and manufactured a full range of traction machines and control equipment for electric vehicles, including electric locomotives and multiple unit trains for main-line and mass-transit railway systems (dc up to 3,000 volts, and ac up to 50,000 volts), diesel-electric locomotives and trains, mining and industrial locomotives, tramcars and trolleybuses. GEC Traction was the leading supplier of traction equipment in the UK and had a wide market around the world, particularly in South Africa, Australasia, Hong Kong, South Korea, South America and Pakistan. In 1979 the Industrial Locomotive Division of the former English Electric which was based at Vulcan Works, Newton-le-Willows was merged into GEC Traction, which later became a separate company, GEC Industrial Locomotives Ltd. During the late 1980s and 1990s the firm underwent major rationalisation, involving closure of several sites including Attercliffe Common in Sheffield in 1985 and the company’s headquarters at Trafford Park in Manchester in 1998. The company name GEC Traction endured until a merger with the French Alsthom group in 1989, which created GEC Alsthom Traction, which was still a branch of the main company GEC Alsthom.

The General Electric Company (GEC) merged AEI Traction Division and English Electric Traction in 1969 after acquiring both companies to create English Electric – AEI Traction Limited. The headquarters were located at Trafford Park in Manchester. This subsidiary company was renamed GEC Traction Limited in 1972.

Metropolitan-Vickers Electrical Co Ltd was the new trading name given to British Westinghouse Electric and Manufacturing Co on 8 September 1919. The predecessor company had sold its controlling share to the Metropolitan Carriage Wagon Co in 1916 in order to gain membership of the Federation of British Industries. In 1919, Vickers acquired the Metropolitan Carriage Wagon Co, along with its controlling share in British Westinghouse, prompting the change in name to Metropolitan-Vickers Electrical Co Ltd. The American owned British Westinghouse had established its English operations at Trafford Park in 1899, and Metropolitan-Vickers Electrical Co Ltd continued on the same site from 8 September 1919. The company was initially known for its electricity generators, later diversifying into the manufacture of steam turbines, switchgear, transformers, electronics and railway traction equipment. The passing of the Electricity (Supply) Act in 1926 provided a boost to the company’s post-war fortunes, with the creation of the National Grid generating demand for the company's products. In 1928, Metropolitan-Vickers Electrical Co Ltd merged with its rival British Thomson Houston Co Ltd, retaining both names for trading purposes. The following year, on 4 January 1929, Associated Electrical Industries Ltd (AEI) acquired Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd. Again, both trading names were retained, and a fierce rivalry was established between the firms which the parent company was unable to control. In 1931, Sir Felix Pole joined Metropolitan-Vickers Electrical Co Ltd as its new chairman. He oversaw a period of expansion for the company leading into the Second World War. In 1939, seeking a more concise name for the company, the Board of Directors decided upon Metrovicks, which became interchangeable with the official company name of Metropolitan-Vickers Electrical Co Ltd. Under Sir Felix Pole's chairmanship, Metropolitan-Vickers developed new products for the aviation industry and during the war was one of the sites where Lancaster bombers were built. In 1941, the company developed the first British axial-flow jet engine, the Metrovick F.2. Following the Second World War, the company appointed Oliver Lyttelton as chairman, with the aim of increasing the efficiency and productivity of AEI. Despite his success in achieving this aim, Lyttelton was unable to resolve the commercial rivalry between Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd. During his second period as chairman, from 1954-1963, Lyttelton, now Lord Chandos, oversaw the development by Metropolitan-Vickers Electrical Co Ltd of the first commercial transistor computer, the Metrovick 950. Chandos also resolved to extinguish the competition and internal divisions between Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd, and both company names ceased to be used from 1 January 1960, with all subsidiaries going on to trade under the name of Associated Electrical Industries Ltd.

In 1959 Associated Electrical Industries (AEI) created a self-contained company named AEI Traction Division to control the railway activities of both Metropolitan Vickers Electrical Company Ltd and British Thomson-Houston (BTH). Included in this company were the interests of the Metropolitan-Vickers General Railway Signal Co., (later to become GEC General Railway Signal). The newly formed company established its headquarters, at Trafford Park, Manchester, and operated from three other sites, Attercliffe Common in Sheffield, Rugby Works, and Stockton Works supplying traction motors, machines, control gear and mechanical parts of locomotives. AEI Traction Limited’s product range encompassed electric and diesel-electric locomotives; electrical equipment for tramcars, trolley buses, trolley mining locomotives, traction motors and gears. In 1969 AEI Traction Division merged with English Electric Traction to form English Electric-AEI Traction Division.

Associated Electrical Industries (AEI) was formed in 1928 as a financial holding company for a number of leading electrical manufacturing and trading companies in the United Kingdom. The two major constituent companies were British Thomson-Houston (BTH) based at Rugby, (Mill Road Works) and Metropolitan-Vickers Electrical Company Ltd (Metrovicks) situated at Trafford Park, Manchester. However, fierce rivalry existed between the Metrovick and BTH brands resulting in internal competition and duplicated management. This was highlighted during the Second World War in 1939, when Metrovicks and BTH became the first two firms in the world to construct jet engines (independently from each other). Following the Second World War, in 1954, AEI expanded to consist of BTH, Metrovicks, Edison Swan Electric Co, Ferguson Pailin, Hotpoint Electric Appliance Co, International Refrigerator Co, Newton Victor, Sunvic Controls, Premier Electric Heaters, Siemens Bros (1955) and Birlec (1954). In 1959 AEI decided to remove the familiar brands of BTH and Metrovicks and consolidate both as AEI resulting in internal problems and a fall in sales and market value. However, AEI acquired a variety of companies from 1959 to 1967, these included Associated Insulation Products, W. T. Henley’s Telegraph Works Co (1958), and London Electric Wire Co and Smiths (1958), Submarine Cables, Hackbridge Holdings Ltd., The Lancashire Dynamo and Crypto Ltd., W.T. Avery Ltd., Henley and Schreiber. The General Electric Company bought AEI in 1967.