<P> The Army had seven main sub-designations for M4 variants during production: M4, M4A1, M4A2, M4A3, M4A4, M4A5, and M4A6 . These designations did not necessarily indicate linear improvement; in that "M4A4" did not indicate it was better than "M4A3 ." These sub-types indicated standardized production variations, which were in fact often manufactured concurrently at different locations . The sub-types differed mainly in engines, although the M4A1 differed from the other variants by its fully cast upper hull, with a distinctive rounded appearance . The M4A4 had a longer engine system that required a longer hull and more track blocks, and thus the most distinguishing feature of the M4A4 was the wider longitudinal spacing between the bogies . "M4A5" was an administrative placeholder designation for Canadian production . The M4A6 had a radial diesel engine as well as the elongated chassis of the M4A4, but only 75 of these were ever produced . </P> <P> While most Sherman sub-types ran on gasoline, (the Continental - produced 350 or 400 hp (261 or 298 kW) Wright R975 Whirlwind 9 cylinder radial gasoline engine, the 450 hp (336 kW) Ford GAA V8 gasoline engine, or the 370 hp (276 kW) 30 cylinder Chrysler A57 multibank gasoline engine) the M4A2 and M4A6 had diesel engines . The M4A2 was powered by a pair of GMC 6--71 two - stroke inline engines, that produced a total of 375 hp (280 kW), while the M4A6 used an RD - 1820 (a redesigned Caterpillar D - 200A radial diesel engine, adapted from Wright Aeronautical's Cyclone 9 nine cylinder radial aircraft engine .) that produced 450 hp (340 kW) The M4A2 and M4A4 were mostly supplied to other Allied countries under Lend - Lease . The term "M4" can refer specifically to the initial sub-type with its Continental radial engine, or generically, to the entire family of seven Sherman sub-types, depending on context . Many details of production, shape, strength, and performance improved while in production, without a change to the tank's basic model number . These included more durable suspension units, safer "wet" (W) ammunition stowage, and stronger or more efficient armor arrangements, such as the M4 "Composite," which had a cheaper to produce cast front hull section mated to a regular welded rear hull . British nomenclature regarding Sherman variants differed from that employed by the U.S. A 24 - volt electrical system was used in the M4 . </P> <Table> M4 Sherman: comparison of key production features of selected models <Tr> <Th> Designation </Th> <Th> Main Armament </Th> <Th> Hull </Th> <Th> Engine </Th> </Tr> <Tr> <Th> M4 </Th> <Td> 75 mm </Td> <Td> welded </Td> <Td> gasoline Continental R975 radial </Td> </Tr> <Tr> <Th> M4 (105) </Th> <Td> 105 mm howitzer </Td> <Td> welded </Td> <Td> gasoline Continental R975 radial </Td> </Tr> <Tr> <Th> M4 Composite </Th> <Td> 75 mm </Td> <Td> cast front, welded sides </Td> <Td> gasoline Continental R975 radial </Td> </Tr> <Tr> <Th> M4A1 </Th> <Td> 75 mm </Td> <Td> cast </Td> <Td> gasoline Continental R975 radial </Td> </Tr> <Tr> <Th> M4A1 (76) W </Th> <Td> 76 mm </Td> <Td> cast </Td> <Td> gasoline Continental R975 radial </Td> </Tr> <Tr> <Th> M4A2 </Th> <Td> 75 mm </Td> <Td> welded </Td> <Td> GM 6046 diesel (conjoined 6 - 71s) </Td> </Tr> <Tr> <Th> M4A3 (75) W </Th> <Td> 75 mm </Td> <Td> welded </Td> <Td> gasoline Ford GAA V8 </Td> </Tr> <Tr> <Th> M4A3E2 "Jumbo" </Th> <Td> 75 mm (some 76 mm) </Td> <Td> welded </Td> <Td> gasoline Ford GAA V8 </Td> </Tr> <Tr> <Th> M4A3 (76) W </Th> <Td> 76 mm </Td> <Td> welded </Td> <Td> gasoline Ford GAA V8 </Td> </Tr> <Tr> <Th> M4A4 </Th> <Td> 75 mm </Td> <Td> welded; lengthened </Td> <Td> gasoline Chrysler A57 multibank </Td> </Tr> <Tr> <Th> M4A6 </Th> <Td> 75 mm </Td> <Td> cast front, welded sides; lengthened </Td> <Td> diesel Caterpillar D200A radial </Td> </Tr> </Table> <Tr> <Th> Designation </Th> <Th> Main Armament </Th> <Th> Hull </Th> <Th> Engine </Th> </Tr>

What kind of engine did the sherman tank have
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