Medium Tank M3 Lee in Camp Polk, Louisiana.

The riveted construction of the medium tank M3 is obvious here. The machine gun in the commander's cupola is present in its right aperture, and one of the driver's hull machine guns has been retained. Track grousers are stored in the box below the driver's hatch, and the tank's siren is positioned below the 75mm gun. Here the crew, Cpl. Larry Corletti, Pvt. Murril Chapman, and Pvt. Louis Robles, practice dismounting from a disabled vehicle. (Picture taken 12 Feb 1943 by Sgt. Calvano; available from the U.S. Army Center of Military History.)

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Medium Tank M3 Lee.

This stylized sketch shows a ghosted glimpse of the interior. The driver's seat is centered in the hull front, and the 37mm gunner was seated in the turret. The commander was provided with positions in the turret rear and the cupola. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The asymmetric design of the tank is highlighted in this top view. A towing cable and tools are stowed on the rear deck, and the filler covers for the four fuel tanks can be seen on each side of the engine air intake grille. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

This early-production tank is fitted with pepperpot-style exhaust mufflers in contrast to the vehicles below. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

A cross-sectional view of the tank is provided in this image. This tank also has the early exhaust and air cleaner setup. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

An early air cleaner assembly is shown here. One could be found at each rear corner of the engine compartment, and they were of the oil bath type. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Cruiser Tank Grant I at the US Army Ordnance Museum.

This tank has the later air cleaner and exhaust system. The rectangular exhaust pipes are now in the center, with the engine's air cleaners in each upper corner. Engine access was provided by the double doors, and the hole in the rear armor was for the engine hand crank. Taillight groups can be seen above the fenders. A pistol port is visible on the superstructure's right side, and an antenna mount is mounted on the opposite side of the superstructure.

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Medium Tank M3 Lee at the Virginia Museum of Military Vehicles.

The air cleaners were vulnerable to damage from enemy fire, so extra protection was added around them.

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Medium Tank M3 Lee at the Virginia Museum of Military Vehicles.

A close-up of the twin exhaust tips is shown here.

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Medium Tank M3 Lee.

1. Driver's seat. 2. Radio operator's seat. 3. 75-mm gunner's seat. 4. 37-mm gunner's seat. 5. 37-mm loader's seat. 6. Tank commander's seat. 8. Cal. .30 machine gun. 9. Cal. .30 machine gun. 10. 37-mm gun. 11. 75-mm gun. 12. 2 cal. .30 machine guns. 13. Protectoscopes. 14. 51 rounds 37-mm ammunition carried in turret. 15. 13 rounds 37-mm ammunition. 16. 11 rounds 37-mm ammunition. 17. 42 rounds 37-mm ammunition. 18. Ten 100-round belts cal. .30 ammunition. 19. 20 rounds 37-mm ammunition. 20. Fourteen 250-round belts containing 225 rounds cal. .30 ammunition. 21. Two 250-round belts containing 225 rounds cal. .30 ammunition. 22. Twenty-five 100-round belts cal. .30 ammunition. 23. 41 rounds 75-mm ammunition; six 100-round belts cal. .30 ammunition. 24. 42 rounds 37-mm ammunition. 25. Submachine gun. 26. Submachine gun. Carried in tank but not shown on drawing are 9 rounds 75 mm ammunition carried in cartons and twenty-four 50-round clips cal. .45 ammunition. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee at the Virginia Museum of Military Vehicles.

The US version of the M3 kept the radio in the hull and featured a large machine gun cupola for the tank commander. The turret consequently had a short overhang, and the TC's cupola is very prominent. In this image, we are looking at the rear of the turret, and the cupola is rotated to almost 9 o'clock. A vision slot is open on the side of the cupola, and a ventilator is visible beside the cupola.

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Medium Tank M3 Lee at the Virginia Museum of Military Vehicles.

The front of the TC's cupola is shown here. The aperture for the .30cal machine gun is on the commander's right side, and a protectoscope was housed in the opposite opening. Below, the opening for the 37mm gunner's periscope M2 can be seen on the turret front.

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Medium Tank M3 Lee at the Virginia Museum of Military Vehicles.

This is a later-production vehicle, as indicated by the ventilators and the lack of side hull doors. The pistol ports and roof hatch over the 75mm gun sponson were retained, however. A stowage box is mounted on the rear deck, and the pistol ports feature protectoscopes.

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Medium Tank M3 Lee.

A cross-section of a protectoscope is drawn here. The user was shielded against incoming fire via the prism that displaced the operator's eyes downward behind armor. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee at the Virginia Museum of Military Vehicles.

The suspension on the M3 was based on that of the medium tank M2. This vehicle is not fitted with the later, heavy-duty volute springs that necessitated moving the track return roller to the rear of the assembly.

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Medium Tank M3 Lee.

The components of a suspension bogie are labeled here. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

Track tension was adjusted by first loosening the two outside clamping bolts that secured the split housing, and the split housing was then opened by turning the spreader bolt. With the split housing loosened, the clip at the end of the spindle was raised, and the collar was driven off of the serrations on the spindle. The idler could then be adjusted by turning the spindle shaft with the appropriate wrench. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

The different turret on this vehicle marks it as a British Grant I. The British did not use the turret machine gun cupola and placed a radio in the bustle of the turret of the Grant. The British turret was lower and wider as a consequence. This vehicle retains the hull side doors, but the hull machine gun ports have been plugged.

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

The profile view of the British turret shows the lengthened radio bustle at the rear.

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Medium Tank M3 Lee.

The left side of the short 75mm gun M2 is shown here. The complete gun weighed 783lb (355kg), and the rifling was a uniform right hand twist with one turn in 25.59 calibers. (Picture from FM 23-95 75-mm Tank Gun M2 (Mounted in Medium Tank M3).)

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Medium Tank M3 Lee.

The automatically-operated vertical sliding breechblock is seen closed in this picture. (Picture from FM 23-95 75-mm Tank Gun M2 (Mounted in Medium Tank M3).)

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Medium Tank M3 Lee.

The breech is diagrammed here in the full open position. (Picture from FM 23-95 75-mm Tank Gun M2 (Mounted in Medium Tank M3).)

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Medium Tank M3 Lee.

The left side of the recoil mechanism is detailed in this image. The gun would recoil ~11.5" (~29.2cm) when fired. Piston rods in the top and bottom recoil cylinders were attached to the breech ring, and were consequently pulled to the rear along with the gun. These pistons were pulled through the hydraulic oil in the cylinders, and the action of the oil flowing through half-round tapered grooves in the piston heads along with the compression of four counterrecoil springs during the rearward movement arrested the motion of the gun. The counterrecoil springs then expanded to return the ordnance to battery. (Picture from FM 23-95 75-mm Tank Gun M2 (Mounted in Medium Tank M3).)

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Medium Tank M3 Lee.

The 75mm gun's horizontal rotor is seen here from the rear. The gun, elevating shield, and recoil mechanism were all supported by the trunnion in the trunnion seats of the rotor, and the entire assembly was supported by a vertical thrust roller bearing on the bottom of the rotor. The horizontal rotor weighed 875lb (397kg). (Picture from FM 23-95 75-mm Tank Gun M2 (Mounted in Medium Tank M3).)

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Medium Tank M3 Lee.

The interior of the 75mm gun's elevating shield is shown in this picture. The elevating shield weighed 442lb (200kg), and extended through the horizontal rotor via the large rectangular cutout in the latter. The elevating shield retained and protected the recoil mechanism, to which it was connected via the recoil mechanism trunnions. The gun tube passed through the circular opening to the front. (Picture from FM 23-95 75-mm Tank Gun M2 (Mounted in Medium Tank M3).)

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Medium Tank M3 Lee.

The short 75mm gun M2 is shown here with the parts of the gun mount labeled. One turn of the traversing handwheel moved the gun by 1°6', and a revolution of the elevation handwheel produced 1°8' of elevation or depression. (Picture from FM 23-95 75-mm Tank Gun M2 (Mounted in Medium Tank M3).)

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Medium Tank M3 Lee.

The 75mm gun mount is seen from the left side. The gunner's seat was fixed and did not follow the gun mount as it was aimed. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

Looking through the open starboard side door, the breech of the 75mm gun and the 75mm gunner's seat is visible. The driver's black padded seat is beyond the 75mm gunner's seat, and the 37mm turret shield is to the 75mm gunner's left rear.

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

A second view of the 75mm gun, including the gunner's periscope M1, is shown here. The piston for the gyrostabilizer is mounted to the right of the 75mm gun, but the rest of the equipment is missing.

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Medium Tank M3 Lee.

The various components of the 75 mm gun stabilizer are outlined here. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

The interior of the tank behind the 75mm gunner is shown here. The engine propeller shaft runs beneath the turret, and an oil cooler and oil tank are attached to the bulkhead. The two gauges facing us above the propeller shaft are fuel gauges, and the red handles are for discharging the carbon dioxide cylinder fire extinguishers. The red fire extinguisher cylinders themselves can be seen under the turret basket.

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

Looking beyond the 75mm gun, we can see the driver's controls and instrument panel. The steering levers are in front of his seat, and the white gear shift lever is to his right. The handwheel on the right of the image is for traversing the 75mm gun, and this handwheel also contained the solenoid firing button. The riveted construction of the vehicle is evident on the inside as well, and the rivets had the unfortunate tendency to break apart when hit and ricochet around the cramped interior of the vehicle.

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Medium Tank M3 Lee.

The driver's controls are detailed in this picture. The driver sat astride the transmission housing, with a foot pedal located on each side and the steering levers bent into a complex shape to provide clearance of the transmission housing. Note the firing switches for the driver's machine guns. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

A closer look at the driver's instrument panel is provided here. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

Details of the mounting of the twin hull machine guns are shown in this image. The guns could be fired by the conventional triggers or by the solenoids activated by the steering lever switches. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The hydraulic turret traversing mechanism is detailed in this picture. The electric motor on the turret floor was directly connected to the hydraulic pump, which drew hydraulic oil from the reservoir on the turret basket wall. The pump delivered the oil under pressure to the inlet port of the manually-operated control valve, which governed the flow of oil through one of two tubes that were connected with the hydraulic motor. Depending on which tube through which the oil flowed, the hydraulic motor turned in one or the other direction. The hydraulic motor's shaft was splined through two pairs of spur gears to a pinion that engaged with the stationary ring gear on the tank hull. The valve control handle could be turned to the right or left to determine the tube through which the oil would flow, and therefore determine the direction of turret rotation. A manual traverse drive was also mounted along with a shifting lever that allowed the traverse to be changed from hydraulic to manual. (Picture from TM 9-1750H Ordnance Maintenance--Hydraulic Traversing Mechanism (Logansport) for Medium Tank M3 and Modifications.)

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Medium Tank M3 Lee.

The manual traversing gear mechanism and hydraulic control valve handle are detailed installed in the turret. (Picture from TM 9-1750H Ordnance Maintenance--Hydraulic Traversing Mechanism (Logansport) for Medium Tank M3 and Modifications.)

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Medium Tank M3 Lee.

A similar view labels instead the controls for the operation of the turret and turret guns. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The hydraulic control valve is shown here. It was a manually-operated two-way piston valve that directed the flow of oil to one side or the other of the hydraulic motor, thereby rotating the turret in the desired direction. Electric switches for firing the turret guns were also mounted on the valve handle. It was necessary to squeeze the trigger, which flipped the safety switch, before the two firing switches were energized. The handle and trigger would return to their neutral positions if they were released, stopping turret traverse and de-energizing the firing switches. (Picture from TM 9-1750H Ordnance Maintenance--Hydraulic Traversing Mechanism (Logansport) for Medium Tank M3 and Modifications.)

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Medium Tank M3 Lee.

The manual traversing gear mechanism was geared to a pinion that meshed with the stationary ring gear on the tank hull. Two pairs of bevel gears and one pair of spur gears were used in the manual traversing mechanism. The shift lever was used to engage either the manual mechanism or hydraulic systems. (Picture from TM 9-1750H Ordnance Maintenance--Hydraulic Traversing Mechanism (Logansport) for Medium Tank M3 and Modifications.)

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

This image is looking into the 37mm turret from the port hull side door. The tank commander's seat is at the top right corner of the picture, the 37mm loader's seat is directly across the turret, the rear of the 37mm gunner's seat can be glimpsed to the left of the frame, and 37mm ammunition racks line the turret walls.

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

The turret crew's positions relative to each other can be better seen here. The gunner's elevation handwheel has a black handle and is positioned parallel to the 37mm gun, and the black gyrostabilizer control unit can be seen across the turret near the turret ring.

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Medium Tank M3 Lee.

A broader view of the turret interior is labeled here. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The parts of the stabilizer for the 37 mm gun are detailed here. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The opposite side of the turret is shown here. The cables hanging down in this image can be seen in the foreground of the picture above. (Picture from FM 23-81 37-mm Gun, Tank, M6 (Mounted in Tanks).)

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Cruiser Tank Grant I at the Virginia Museum of Military Vehicles.

Details of the commander's hatch are shown here. A rotatable periscope mount is allowing light through.

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Medium Tank M3 Lee.

A top-down view of the engine compartment is the subject of this image. The front of the hull is to the top of the picture. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The R975 EC2 engine is seen from the left front. The flywheel end of the engine was considered the front, and the right and left sides were determined by looking at the engine from the rear. (Picture from TM 9-1751 Ordnance Maintenance--Wright Whirlwind Engine Model R975EC-2.)

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Medium Tank M3 Lee.

The engine is shown from the left rear. Bore and stroke were 5.50" and 5.50" (12.7cm and 14.0cm), respectively, for a displacement of 973in³ (15.9L). (Picture from TM 9-1751 Ordnance Maintenance--Wright Whirlwind Engine Model R975EC-2.)

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Medium Tank M3 Lee.

The engine's rear is labeled in this image. The top cylinder was number one, and the rest were sequentially numbered clockwise. Firing order was 1, 3, 5, 7, 9, 2, 4, 6, and 8. (Picture from TM 9-1751 Ordnance Maintenance--Wright Whirlwind Engine Model R975EC-2.)

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Medium Tank M3 Lee.

The transmission featured synchromesh second through fifth gears, and constant mesh for first and reverse. A parking brake was built into the transmission, and was actuated by the lever to the left of the image. The gearshift lever is on the opposite side of the transmission. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

Four fuel tanks for the main engine were located in the hull rear. The auxiliary generator was provided with its own 2.5gal (9.5L) fuel tank in the left rear of the fighting compartment. The 2-cycle auxiliary generator engine required ⅜ pint (180mL) of SAE 50 or 60 engine oil to be mixed with each gallon (3.8L) of gasoline. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

Two 12-volt storage batteries were connected in series to provide for the 24-volt electrical system. The battery compartment was behind the driver on the hull's left side under the turret basket. The radio switch had its own connection to the battery. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

Two cylinders each containing 10lb (4.5kg) of CO2 comprised the fixed fire extinguishing system. These were routed to the engine compartment, and two 4lb (2kg) portable fire extinguishers were carried for fires in other locations. The fixed system was entirely manual; control handles were provided at the turret basket bracket, near the fuel gages, and on the exterior of the top of the engine compartment. If a second cylinder needed to be actuated, another handle would have to be pulled. The fixed extinguisher control head and cylinder valve are shown on the left, with the control head detailed on the right. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The tank's auxiliary generator, the Homelite heater-generator HRH-28, was mounted in the left rear corner of the fighting compartment. It supplied 1500 watts, 30 volts DC for charging the tank's batteries; and a heater element preheated the main engine as well as provided heat for the crew. The Homelite HR-28 electrical generator was driven by a small 3400-3600rpm, 2-cycle, single-cylinder Homelite HR gasoline engine. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The rear of the auxiliary generator is shown here. It was desirable to operate the generator when the turret was being operated via hydraulic power or when the guns were being fired, since all except the cupola .30cal machine gun were triggered via solenoids. (Picture from TM 9-750 Medium Tanks M3, M3A1, and M3A2.)

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Medium Tank M3 Lee.

The control box had buttons for START, BATTERY, and HEATER. The battery and heater buttons used the generator towards charging the vehicle batteries and powering the heater element, respectively, while the start button started the generator engine electrically. If necessary, a starting rope could also be used to start the engine after removing the magneto shield. (Picture from TM 9-1752 Ordnance Maintenance--Auxiliary Generator (Homelite Model HRH-28) for Medium Tanks M3.)

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Medium Tank M3A1 Lee.

This cast, smooth-lined M3A1 is armed with the short-barreled 75mm gun M2, and since neither it nor the 37mm guns are fitted with counterweights, this tank also lacks stabilization. This tank also has the early suspension bogies which have the return roller on top of the brace. The aperture to the left of the 37mm gun was for the gunner's periscope. The machine gun in the cupola emerged from the right opening; the left was for a vision slot. There are antenna mounts behind the turret and behind the front hull pistol port. (Picture from Tank Data, vol. 2.)

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Medium Tank M3A1(diesel) Lee.

The front of a T-1400-3 diesel engine is seen here; it differed from the T-1400-2 by having a cylinder barrel with an 8 ⅜" (21.27cm) outside diameter compared to the earlier engine's 7 ½" (19cm) outside diameter. Bore and stroke were 5 ¾" and 6" (14.6cm and 15cm), respectively, for a displacement of 1,402in³ (22.97L). (Picture from TM 9-1750E Ordnance Maintenance--Guiberson Diesel T1400 Engine, Series 3, for Medium Tanks M3 and M4 and Related Gun Motor Carriages.)

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Medium Tank M3A1(diesel) Lee.

The T-1400 is shown from the rear. Its overall diameter was 53" (135cm), and length with Coffman starter and 30-watt generator installed was 41 ⅞" (106.36cm). Compression ratio was 14:1, and it produced 350-375bhp at 2,200rpm. (Picture from TM 9-1750E Ordnance Maintenance--Guiberson Diesel T1400 Engine, Series 3, for Medium Tanks M3 and M4 and Related Gun Motor Carriages.)

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Medium Tank M3A1(diesel) Lee.

Fuel oil was forced from the tanks and through the filter by the fuel supply pump. From there, a one-way check valve permitted entry into the fuel channel, which was a drilled passage in the rear mounting section of the crankcase that connected the injection pump mounting holes. The channel supplied each fuel injection pump with fuel that was then passed through the injectors into the combustion chambers. A. Tank vent. B. Fuel tank. C. Tank valve. D. Fuel oil filter. E. Supply pump. F. One way check valve. G. Fuel channel. H. Injection pump. I. Pressure line. J. Injector. K. Drip line. L. Fuel return ring. M. Regulator valve. N. Return line. (Picture from TM 9-1750E Ordnance Maintenance--Guiberson Diesel T1400 Engine, Series 3, for Medium Tanks M3 and M4 and Related Gun Motor Carriages.)

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Medium Tank M3A2 Lee.

The M3A2 was the first of the series to feature a welded hull. The sharp lines and lack of riveting are obvious when compared with the tanks above. (Picture from Tank Data, vol. 2.)

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Medium Tank M3A5 Lee.

Most of the identifying features for M3A5 are on the rear of the vehicle, since the major difference between M3A5 and M3 is that the former is powered by twin diesel engines rather than the radial gasoline engine. This tank is not fitted with stabilization since it lacks counterweights under the 37mm gun and around the end of the short 75mm gun M2's barrel. It also is running on the T49 parallel bar steel tracks. (Picture from Development of Armored Vehicles, volume 1: Tanks.)

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Medium Tank M3A5 Lee at the US Army Ordnance Museum.

This later-production tank has its side door welded up, and the pistol port has also been eliminated on this side. The engine air inlet grille is open, and can be seen behind the stowage box.

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Medium Tank M3A5 Lee at the US Army Ordnance Museum.

The tank is fitted with gun stabilizers. The cylindrical counterweight is mounted under the 37mm gun, and the short barrel of the 75mm gun M2 has a counterweight fitted around it. Note the pistol port in the right hull side remained even after the doors had been eliminated.

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Medium Tank M3A5 Lee.

The different internal arrangement necessitated by the twin diesel engines can be gleaned when this image is compared with the cross-section of the M3 above. (Picture from Tank Data, vol. 2.)

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Medium Tank M3A5 Lee.

This is a ¾ front view of the GM 6046 power unit. The power from each engine was sent through its drive shaft and gear to a common driven gear which in turn drove the propeller shaft. The individual engines were designated model 671LA24M (right-side engine) and 671LC24M (left-side engine), abbreviated LA and LC, respectively. The power unit weighed 4,340lb (1,970kg), and the weight as installed including the radiators, filter panel, voltage and current regulator, propeller shaft, fan shrouds, and exhaust mufflers was 4,855lb (2,202kg). This early engine has the original three-blade cast cooling fans. Note also the single generator, which is the black cylinder protruding horizontally from the near corner. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee.

The early fans can be better seen from this angle. The engines' bore and stroke were 4.25" and 5" (10.8cm and 12.7cm), respectively, for a displacement of 425in³ (6.96L) for each engine. The nominal compression ratio was 16:1. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee.

The fans were changed during production to five-blade assemblies assembled from stamped steel. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee.

The five-blade fans are visible from this angle. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee.

The legend for this cross-sectional view is as follows: 1. Oil cooler adapter. 2. Oil cooler. 3. Blower housing. 4. Blower rotors. 5. Air cleaner. 6. Secondary fuel filter. 7. Camshaft. 8. Rocker arm. 9. Injector. 10. Injector control rack tube lever. 11. Water outlet manifold. 12. Exhaust manifold. 13. Balancer shaft. 14. Valve rocker cover. 15. Push rod. 16. Section of piston and connecting rod. 17. Air box. 18. Solenoid air inlet control. 19. Air inlet housing. 20. Connecting rod bearing shell. 21. Crankshaft. 22. Main bearing shell. 23. Lubricating oil pump assembly. 24. Lubricating oil pump driven gear. 25. Air heater. 26. Air heater fuel pipe. 27. Clutch shift levers. (Picture from TM 9-1750G Ordnance Maintenance--General Motors Twin Diesel 6-71 Power Plant for Medium Tanks M3A3, M3A5, and M4A2.)

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Medium Tank M3A5 Lee.

An LC engine is sectionalized in this drawing. 1. Vibration damper. 2. Air heater cover. 3. Handhole cover. 4. Camshaft bearing (Plain) (Thrust on LA). 5. Camshaft. 6. Fan drive gear train. 7. Fan assembly. 8. Thermostat housing. 9. Exhaust manifold. 10. Water outlet manifold. 11. Injector control tube and bracket assembly. 12. Injector assembly. 13. Exhaust valve spring. 14. Exhaust valves. 15. Sectional view of piston and connecting rod assembly. 16. Cylinder liner. 17. Valve rocket cover. 18. Fuel pipe. 19. Exhaust and injector rocket arm assemblies. 20. Push rods. 21. Lifter bracket assembly. 22. Cam follower. 23. Cam. 24. Camshaft bearing (Thrust) (Plain on LA). 25. Camshaft gear. 26. Idler gear. 27. Flywheel. 28. Clutch pressure plate. 29. Clutch spring. 30. Clutch release spring. 31. Engine drive gear. 32. Transfer gear housing. 33. Clutch housing. 34. Engine drive shaft. 35. Flywheel housing. 36. Crankshaft gear. 37. Oil pan. 38. Cylinder air inlet port. 39. Cylinder wall. 40. Main bearing. 41. Connecting rod bearing. 42. Lubricating oil pump assembly. 43. Cylinder block. 44. Lubricating oil pump gear train. 45. Crankshaft. (Picture from TM 9-1750G Ordnance Maintenance--General Motors Twin Diesel 6-71 Power Plant for Medium Tanks M3A3, M3A5, and M4A2.)

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Medium Tank M3A5 Lee.

An exploded view of the power transfer unit is shown here. Power was delivered to the transfer unit from each engine via a heavy-duty 16" (41cm) dry disc clutch at each engine flywheel. Each clutch had its own throw-out lever, allowing either one to be manually locked out from the driver's position so that the tank could operate on a single engine if needed. The clutches' driven plates were splined to drive shafts, each with a helical gear that meshed with a single gear on the driven shaft that led to the propeller shaft and transmission. Early engines were built with 80-tooth drive gears and 67-tooth driven gears (1:1.19), while later engines had 85-tooth drive gears and 62-tooth driven gears (1:1.37), which increased the vehicle speed from 25 to 29mph (40 to 47kph) at 2100rpm. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee.

The assembled power transfer unit is the subject of this diagram. 1. Driven gear (67 teeth). 2. Drive gear (80 teeth). 3. Transfer case housing. 4. Clutch housing. 5. Engine driven shaft flange. 6. Flywheel housing. 7. Flywheel. 8. Crankshaft. 9. Engine drive shaft. 10. Engine driven shaft. 11. Clutch spring assembly. 12. Shifter yoke. 13. Clutch shifter shaft. 14. Driven disc hub 15. Clutch spring hub. 16. Clutch release bearing sleeve. 17. Clutch release bearing sleeve guide. 18. Rear oil slinger (large). 19. Clutch release bearing sleeve cover. 20. Front oil slinger (small). 21. Grease retainer. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee.

The tubular propeller shaft was a Spicer heavy-duty needle bearing unit. Late-production tanks featured a slightly longer propeller shaft with a diameter increased to 4" (10cm) from 3.5" (8.9cm). 1. Circular flange yoke. 2. Sleeve yoke assembly. 3. Journal cross or trunnion. 4. Needle bearing assembly. 5. Bearing cap. 6. Splined stub shaft. 7. Shaft tube. 8. Relief valve--each end. 9. Gasket. 10. Gasket retainer. 11. Lock strap. 12. Stub ball yoke. 15. Pipe plug--splined joint. 16. Aligning arrows. 17. Dust cap. 18. Cork washer. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee.

A single Model S-2 (military) replaceable-type lubricating oil filter was used for each engine, and these were mounted on an accessory panel at the front of the engine compartment. The components of the accessory panel were: 1. Primary fuel filter. 2. Heater coil box. 3. Filter panel. 4. Lubricating oil filter. 5. Auxiliary starter switch. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee at the US Army Ordnance Museum.

Looking forward into the open engine compartment, the connections for the filters on the accessory panel can be seen on the front wall. The valve rocker covers for the two engines are low in the engine compartment, and between them are the water outlet and exhaust manifolds. Two cylindrical air cleaners are just visible at the lower corners of the opening.

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Medium Tank M3A5 Lee.

The exhaust system was composed of two exhaust manifolds, two mufflers each with a support bracket, two 90° elbows, and two exhaust pipes. 1. Exhaust manifold. 2. Exhaust gasket. 3. Exhaust elbow. 4. Exhaust pipe. 5. Exhaust muffler support bracket. 6. Exhaust muffler. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A5 Lee.

The driver's instrument panel is labeled here. 1. Throttle control--LC engine. 2. Throttle control--LA engine. 3. Throttle lock. 4. Instruction plate--air heater. 5. Clutch lockout--LA engine. 6. Clutch lockout--LC engine. 7. Air heater pump--LA engine. 8. Air heater pump--LC engine. 9. Tell-tale (warning light)--air heater switch--LA engine. 10. Tell-tale (warning light)--air heater switch--LC engine. 11. Air heater switch--LA engine. 12. Air heater switch--LC engine. 13. Tachometer--LA engine. 14. Switch--panel lights. 15. Pressure gage--lubricating oil--LA engine. 16. Tell-tale (warning light)--low lubricating oil pressure--LA engine. 17. Tachometer--LC engine. 18. Tell-tale (warning light)--low lubricating oil pressure--LC engine. 19. Pressure gage--lubricating oil--LC engine. 20. Reset lever--speedometer. 21. Ammeter. 22. Switch--windshield wiper. 23. Outlet--windshield wire lead. 24. Outlet--defroster lead. 25. Instruction plate--lights. 26. Switch--running lights. 27. Switch button--emergency stop--LC engine. 28. Switch button--emergency stop--LA engine. 29. Switch button--starting--LC engine. 30. Switch button--starting--LA engine. 31. Clock. 32. Voltmeter. 33. Speedometer. 34. Gage--water temperature--LC engine. 35. Gage--water temperature--LA engine. (Picture from Model 6046 Series 71 Twin 6 Cylinder Diesel Engine Maintenance Manual.)

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Medium Tank M3A3 Lee.

Compared to the sharp-edged hull machines above, the relative lack of rivets due to welding much of this vehicle is obvious. (Picture from Tank Data, vol. 2.)

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

The dearth of rivets caused by the use of welding is well illustrated by looking at the side of the tank. This vehicle is a later-production example, as the side door has been welded closed.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

A closer view of the welded shut side door and pistol port are provided in this picture.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

Welding the hull did not eliminate all rivets, but their use was drastically reduced.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

Although the side doors have been welded shut, the tank retains apertures for both hull machine guns.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

Details of the counterweight on the 75mm gun M2 are provided here.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

The counterweight for the 37mm gun, however, is not present on this tank, although its aperture remains unplugged.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

The rear deck featured twin armored air intake louvres protected by mesh screens. Filler cap covers can be seen on the rear deck and in front of the sponson stowage boxes for fuel, water, and lubricating oil.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

The rear armor was extended downward compared to radial-engine tanks, and the rear engine access doors were necessarily deleted.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

The mufflers for the engines met in the center of the rear of the vehicle, and a deflector was mounted to keep the exhaust gases from stirring up too much dust. The solid lower rear hull can be contrasted with the radial-engined tank above.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

The reason for the changes to the rear armor was that the radiators for the GM 6046 were mounted at the rear above the mufflers, a concern that tanks powered by the air-cooled radials did not have.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

This picture is looking forward from the rear of the tank. The long rectangular engine inspection plates can be seen in the foreground, each with a round cover for engine oil drain plug access. Since this tank has no side hull doors, it was equipped with a floor escape hatch, the opening for which which can be seen in front of the right-hand engine inspection plate.

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Medium Tank M3A3 Lee belonging to the US Army Armor and Cavalry Collection.

Looking straight up into the escape hatch opening, the front of the tank is to the right of the image. The transfer case can be seen to the left, and the propeller shaft runs off to the right to engage the transmission. Control linkages are near the bottom of the image, and a 75mm ammunition rack can be seen to the right. The underneath of the turret basket is directly overhead.

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Medium Tank M3A4 Lee.

The large Chrysler multibank engine installed in M3A4 necessitated a longer hull to fit in the tank. The distance between the bogies was also therefore increased, and the rear deck roof and engine compartment floor had bulges to accommodate the A57 engine. (Picture from Development of Armored Vehicles, volume 1: Tanks.)

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Medium Tank M3A4 Lee.

The distributor end of the A57 is shown here. A. Tube, water pump air relief (engine no. 1 to no. 2). B. Coil, ignition, assembly (no. 1 engine). C. Cleaner, air, crankcase ventilator, assembly. D. Shaft, drive, tachometer. E. Pump, water, assembly (no. 1 to no. 5 engine). F. Tube, water pump air relief (no. 1 engine). G. Filter, oil (absorption type). H. Coil, ignition (no. 5 engine). I. Pipe, exhaust (nos. 4 and 5 engines). J. Tube, fuel pump to branch connection, assembly (for nos. 4 and 5 carburetors). K. Connection, water pump air relief tube. L. Pump, water, assembly (no. 5 engine). M. Distributor, ignition, assembly (no. 5 engine). N. Tube, water pump air relief (no. 4 to no. 5 engine). O. Tube, fuel pump to no. 1 carburetor, assembly. P. Plate, serial number, engine. Q. Pump, fuel, assembly. R. Coil, ignition, assembly (no. 4 engine). S. Support, engine, rear. T. Pump, water, assembly (no. 4 engine). U. Tube, radiator outlet, assembly (nos. 4 and 5 engines). V. Distributor, ignition, assembly (no. 4 engine). W. Pan, oil. X. Plug, drain, oil pan. Y. Tube, fuel pump to branch connection, assembly (for nos. 2 and 3 carburetors). Z. Distributor, ignition, assembly (no. 3 engine). AA. Pump, water, assembly (no. 3 engine). BB. Tube, radiator outlet, assembly (nos. 2 and 3 engines). CC. Coil, ignition, assembly (no. 3 engine). DD. Cock, drain, cylinder water jacket, assembly. EE. Distributor, ignition, assembly (no. 2 engine). FF. Tube, water pump air relief (no. 2 to no. 3 engine). GG. Pump, water, assembly (no. 2 engine). HH. Coil, ignition, assembly (no. 2 engine). II. Distributor, ignition, assembly (no. 1 engine). JJ. Generator, assembly. KK. Pipe, exhaust (nos. 1, 2, and 3 engines). (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

The power unit's left side is labeled in this picture. Bore and stroke were 3.4375" (8.7312cm) and 4.5" (11cm), respectively, for a displacement of 1,253.0in³ (20.533L). The compression ratio was 6.2:1, and weight with accessories was 5,375lb (2,438kg). (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

The right side is shown here. A. Filter, oil, w/clamp, assembly. B. Carburetor, assembly (no. 5 engine). C. Rod, choke, assembly (no. 5 to no. 4 carburetor). D. Rod, throttle control, assembly (from no. 4 to no. 5 carburetor). E. Tube, carburetor to air cleaner, upper, right, assembly. F. Hose, crankcase vent air cleaner outlet pipe. G. Rod, brace, radiator to engine assembly. H. Radiator assembly. I. Unit, sending, engine water temperature gage, assembly. J. Unit, sending, engine water temperature warning indicator, assembly. K. Unit, sending, exhaust stack temperature warning indicator, assembly. L. Hose, engine to oil cooler (engine end). M. Support, engine, front, right. N. Hose, oil tank to engine (engine end). O. Tube, radiator outlet, assembly. P. Stud, attaching, carburetor adapter elbow. Q. Elbow, adapter, carburetor. R. Governor, carburetor, assembly. S. Carburetor, assembly (no. 4 engine). T. Connection, branch, fuel pump to nos. 4 and 5 carburetor tube. U. Pipe, exhaust, upper, right, assembly. V. Filter, fuel, carburetor, assembly. (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

The top of the power unit can be seen in this picture. Overall length, width, and height were 54.125" (137.48cm), 58.75" (149.2cm), and 56.5" (144cm), respectively. (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

The power unit is shown here from the bottom left. (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

Two outward-opening doors could be found in the lower rear hull for engine access, and the power unit is viewed through this opening. (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

The five engines were assembled to a one-piece cast-iron crankcase, with oil passages cast and drilled into it. An oil pan and a sump were attached to the bottom. In this sketch, the accessory drive shaft, fuel pump drive assembly, and oil pumps are shown in position in the crankcase. A. Shaft, drive, fuel pump. B. Sleeve, accessory drive shaft. C. Washer, thrust, accessory drive shaft gear. D. Gear, accessory drive shaft. E. Gear, accessory drive shaft. F. Washer, thrust, accessory drive shaft gear. G. Shaft, drive, accessory. H. Gear, oil scavenger pump drive shaft. I. Washer, thrust, oil scavenger pump drive shaft gear. J. Shaft, drive, oil scavenger pump. K. Washer, thrust, oil scavenger pump drive shaft. L. Washer, oil scavenger pump drive shaft. M. Pump, scavenger, oil, assembly. N. Support, accessory drive shaft. O. Pump, pressure, oil, assembly. P. Washer, oil pressure pump drive shaft. Q. Washer, thrust, oil pressure pump drive shaft. R. Shaft, drive, oil pressure pump. S. Washer, thrust, oil pressure pump drive shaft gear. T. Gear, oil pressure pump drive shaft. U. Drive, fuel pump, assembly. (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

Engines nos. 4 and 5 are shown assembled to the crankcase, with engine no.3 being lowered into position. With the oil pan yet to be attached, the oil pumps at the bottom of the crankcase can be seen. (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

An interior view of the power unit drive gear housing is provided here. Each engine drive gear was bolted to the end of its engine's crankshaft, and these five drive gears drove the engine power unit driven gear, which was keyed to the power unit driven gear shaft, which drove the engine clutch. (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Medium Tank M3A4 Lee.

The empty power unit compartment is shown in this picture. A. Bracket, engine front support, left. B. Tube, fire extinguisher floor elbow to left floor tee, assembly. C. Bracket, throttle control cross shaft, left, assembly. D. Cable, choke control, assembly. E. Tube, outlet, fuel tank, left, front, assembly. F. Cooler, oil, transmission, assembly. G. Screw, stop, throttle control cross shaft. H. Tube, fire extinguisher bulkhead tee to left front tee, assembly. I. Screen, auxiliary generator exhaust. J. Cable and conduit, battery box to engine harness connector, assembly. K. Cable and conduit, starter and generator, assembly. L. Nozzle, fire extinguisher tube, left, front. M. Tube, auxiliary generator muffler outlet, w/elbow, assembly. N. Conduit, ignition coil mainfeed cable. O. Opening, carburetor air cleaner. P. Conduit, fuel gage, tail and stop light cables. Q. Nozzle, fire extinguisher tube, right, front. R. Opening, carburetor air cleaner. S. Tube, engine oil cooler to oil air remover tube, assembly. T. Tube, fire extinguisher right front tee to nozzle, assembly. U. Cooler, oil, engine, assembly. V. Tube, hose, oil tank to air vent tube. W. Yoke, rear propeller shaft universal joint flange, rear. X. Bearing, throwout, clutch. Y. Tube, outlet, fuel tank, right, front, assembly. Z. Connector, oil cooler to radiator oil hose. AA. Hopper, oil tank assembly. BB. Yoke, clutch release lever. CC. Wire, control, fuel line shut-off valve, right, assembly. DD. Connection, oil tank to radiator oil hose. EE. Cable, tachometer, assembly. FF. Wire, control, fuel line shut-off valve, left, assembly. (Picture from TM 9-1750F Ordnance Maintenance--Power Unit for Medium Tanks M3A4 and M4A4.)

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Last updated 15 Mar 2022.
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