Indian Locomotive Manufacturers
Early locos (late 19th century) were almost all imported. The first steam locomotive was built in India in 1895 at the Ajmer workshops.
Details of some of the more important manufacturers are to be found in the section on production units and workshops.
CLW: Large-scale loco production in India did not begin until the establishment of the Chittaranjan Locomotive Works (CLW) in 1950. More details on CLW here.
DLW: The Diesel Loco Works set up at Varanasi began producing diesel locos in 1967, and has since then produced a large number of mainline and shunter diesels. Variants of various classes in the WDS and WDG series are supplied to industrial concerns as well. More details on DLW here.
BHEL: Bharat Heavy Electricals Ltd. (BHEL) supplied some WAG-5 and three NBM-1 units in the ’80s, and more recently has suplied WCAM-2′s, WCAM-3′s, WAG-8′s, and NDM-6′s. BHEL also makes electrical transmission components, traction motors, alternators, and other components for both three-phase and tap-changer locomotives. The locomotives are made at BHEL’s facilities at Bhopal and Jhansi. Recently  BHEL has entered an agreement with IR to supply several dozen high-horsepower locomotives. As its expertise extends currently only to 6,000hp diesel locos, BHEL is exploring foreign partnerships with GE, Toshiba, and others for production of 10,000hp locomotives.
DCW: Diesel Components Works, Patiala – now renamed the Diesel Modernization Works or DMW, supplies components for some locomotives to DLW. It also works on rebuilding and upgrading locos (e.g., older WDM-2′s being converted to WDM-3A locos). More details on DCW here.
NGEF and Crompton Greaves are other domestic suppliers of traction motors, alternators, etc.
TELCO: Tata Electrical and Locomotive Co. (TELCO) supplied some YP and YG units in the 50′s and 60′s.
Cummins India makes the diesel engines for DMU’s, HPDMU’s, and some MG locos.
Suri and Nayar (SAN), located in Bangalore, have supplied some shunters and other locos, and parts such as transmissions.
Ovis Loco, based in Hyderabad supplies some shunting locos (mainly for industrial customers).
Venkateshwara Transmissions (Ventra) of Medak (Andhra Pradesh) is another manufacturer who supplied some locomotives and locomotive parts to IR.
ICF: Integral Coach Factory has been making EMUs for suburban systems (e.g., the YAU-1 MG 4-car EMU) since 1966. It also makes some self-propelled special-purpose units, such as the diesel Medical Relief Van and diesel-electric tower cars. More details on ICF here.
Bharat Earth Movers Limited (BEML) Formerly a state owned enterprise, Bangalore-based BEML manufactures heavy engineering products, including a wide variety of Railway vehicles made at its Bangalore and Mysore facilities. BEML makes coaches based on the standard ICF type design. A recent addition to the company’s lineup were high tech trainsets (broad gauge and (as of [8/09]) standard gauge) destined for the Delhi Metro. DMRC rolling stock is manufactured in technical collaboration with the Korean firm ROTEM. In addition, BEML also manufactures Railbuses, OHE vans and track-laying equipment. BEML had manufactured coaches for the now scrapped MG EMUs service in Chennai. The company is very likely to supply coaches for planned Metro systems in Bangalore, Mumbai and other places.
Bombardier Transportation makes train-sets for the Delhi Metro at its plant in Vadodara, Gujarat.
The Jamalpur Workshop of ER manufactures diesel self-propelled units such as cranes for clearing wreckage and construction work. More details on Jamalpur here.
The Izzatnagar Works manufactures railbuses and railcars using Ashok Leyland Iveco engines, and Hindustan Motors or Kirloskar Pneumatics converters and transmissions.
Jessop & Co., an engineering company founded in 1788 (and now in the public sector) has manufactured wagons, cranes, and EMU rakes (many of the old EMU rakes in the Calcutta and Mumbai systems were built by Jessop). More details on Jessop here.
Parel Workshops of CR has been assembling BG diesel locomotives since 2006, mostly WDS-6 class shunters, using components from DLW, DCW, and elsewhere. Between 2006 and 2009 it manufactured about 88 such locomotives, about half of which went to private companies (industrial shunters) while the others were purchased by IR.
 A new diesel locomotive production facility has been proposed to be set up at Marhora (Marhowra) in the Saran district of Bihar, near Chhapra. IR is expected to procure 1000 diesel locos of varying power capacities (4,500hp-6,000hp) from this factory over 10 years. This is expected to be a joint venture with a private (foreign or Indian) manufacturing entity – GE and EMD are considered candidates [2/09].
 A new electric locomotive production facility has been proposed to be set up at Madhepura in Bihar, with a capacity to produce 120 locos a year. IR is expected to procure 800 electric locos of 12,000hp power capacity from this factory over 10 years. This is expected to be a joint venture with a private (foreign or Indian) manufacturing entity – Siemens, Alstom, and Bombardier are considered candidates [2/09].
There are many foreign suppliers of early locos: dozens of manufacturers are represented, including Bagnall, Beyer-Peacock, Vulcan Foundry, Nasmyth Wilson, SLM, Kerr-Stuart, Henschel, Hunslet, Dubbs & Co. (Glasgow), Metropolitan Carriage and Wagon Works, Sentinel Carriage and Wagon Works (Shrewsbury), Freid Krupps, Sharp Stewart, Kitson-Meyer, Kawasaki, General Electric, etc.
More recent foreign suppliers of locos include Alco (WDM-1, some WDM-2, some YDM-4), GM (WDG-1, WDM-4, YDM-3, YDM-5), English Electric (WCM-1, WCM-2), Henschel (WDM-3), Maschinenbau Kiel (WDS-3, ZDM-2), Montreal Loco Works (YDM-4A), Hitachi (WCM-3, WCM-4, some WAG-2), Mitsubishi (WAM-2, WAM-3, YAM-1, some WAG-2), Asea Brown-Boveri (WAP-5, some WAG-9), Toshiba (some WAG-2), Krupp (some WAM-1), Alsthom (some WAM-1), Kraus-Maffei (some WAM-1), General Motors EMD (WDP-4, WDG-4, some WDM-4), and Arn. Jung (NDM-1).
Cranes and other equipment have been supplied by Gottwald, Sheldon, ABB, etc. Jamalpur workshops makes many kinds of break-down cranes.
Tower cars and track and OHE inspection vehicles are manufactured by CLW and Jamalpur Workshops.
Industrial locomotives of various kinds were supplied by Andrew Barclay, Brookville, Baldwin, Henschel, Canadian Loco. Co., Greenwood Batley, Ruston & Horsnby, TELCO, Arn. Jung, Kraus-Maffei, GE, and many others.
(Information from the WDL mailing list, posted by John Middleton. Reference: Vitaly Rakov, Locomotives of our country’s railways, 1995, Moscow, ISBN 5-277-00821-7.)