Ordnance Maintenance: Power Unit for Medium Tanks M3A4 and M4A4 - TM 9-1750F War Department Technical Manual

a. This manual is published for the information and guidance of ordnance maintenance personnel. It contains detailed instructions for inspection, disassembly, assembly, maintenance, and repair of the power unit for Medium Tanks M3A4 and M4A4, supplementary to those in the field and technical manuals prepared for the using arms. Additional descriptive matter and illustrations are included to aid in providing a complete working knowledge of the materiel. a. The power unit consists of 5 L-head, water-cooled engines mounted radially on a common crankcase. These power units are used in the Medium Tanks M3A4 and M4A4. a. Power units are numbered serially. All power units used in the Medium Tank M3A4 and in medium tanks with serial numbers M4A41001 to M4A4-2304 inclusive, incorporate multiple water pumps, one mounted on each engine (figs. 1 and 2). Power units of the Medium Tank M4A4 with serial numbers following M4A4-2304 incorporate a single water pump (mounted on the distributor end of the crankcase (fig. 31. On power units equipped with multiple water pumps, the generator is mounted on No. 2 engine and driven by the No. 2 engine water pump belt (fig. 1). The fuel pump is mounted on the distributor end of the crankcase and driven by the accessory shaft (fig. 1). On power units equipped with the single water pump, the generator is mounted in the fighting compartment and belt driven from the propeller shaft. The fuel pump is mounted on the distributor end of No. 4 engine and driven by the camshaft (fig. 3). Power units of Medium Tank M4A4 with serial numbers M4A4-1001 to M4A4-3211 inclusive, are equipped with thermostats in the cooling system, mounted in the engine water outlet adapter of each engine. A bypass type of thermostat, mounted in the radiator inlet adapters of engines Nos. 2, 3, 4, and 5 and in the cylinder head adapter of No. 1 engine entered production on power units starting with serial numbers M4A4-3211 of Medium Tank M4A4 (fig. 195). The clutch, of the fully enclosed type, was used in production of the power unit of the Medium Tank M4A4 with serial numbers from M4A4-1001 to M4A4-4412 inclusive (fig. 6). Beginning with the power unit for the Medium Tank M4A4 above serial numbers M4A4-4413, a clutch of the ventilated type entered production. a. Scope. The scope of maintenance and repair by the crew and other units of the using arms is determined by the availability of suitable tools, availability of necessary parts, capabilities of the mechanics, time available, and the tactical situation. All of these are variable and no exact system of procedure can be prescribed. b. Allocation Of Maintenance. Indicated below are the maintenance duties for which tools and parts have been provided for the using arm personnel. Other replacements and repairs are the responsibility of ordnance maintenance personnel but may be performed by using arm personnel when circumstances permit, within the discretion of the commander concerned. Echelons and words as used in this list of maintenance allocations are denned as follows: Second Echelon: Line organization regiments, battalions, companies, detachments, and separate companies. Third Echelon: Ordnance light maintenance companies, ordnance medium maintenance companies, ordnance divisional maintenance battalions, and post ordnance shops. Fourth Echelon: Ordnance heavy maintenance companies, and service command shops. Fifth Echelon: Ordnance base regiments, ordnance bases, arsenals, and manufacturers' plants.

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