Armored Infantry Vehicle M75.

This machine is one of the earlier vehicles that retained sand shields and recesses for the external fire extinguisher controls, which can be seen just ahead of the fan exhaust grille on the side. The right headlight brushguard has been extended to protect the engine exhaust pipe, however. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The early-production vehicle without the extended brush guard can be seen here head-on. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The left side of an early machine is shown in this image. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The auxiliary generator and engine access door as well as the four visible shock absorbers are hallmarks of an early-production machine. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The two rear doors for infantry entry and exit are obvious in this rear view. Stowage for water cans and pioneer tools can also be seen on the vehicle's rear. Towards the front of the vehicle, the semicircular indentation housing a handle is the auxiliary generator and engine access door. This early machine features the spout-type rear fuel filler and the taillights, exterior fire extinguisher handles, and handle for the side engine access doors are all placed in indentations in the armor. Note the early placement of the handles for the rear doors. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

This upper view is of an early-production vehicle. The brush guard does not protect the engine exhaust pipe, and behind the exhaust pipe on the vehicle's right is the auxiliary engine access cover that was not needed on later vehicles that lacked the auxiliary generator. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

Early vehicles had drain valves in the engine compartment floor and the hull floor under the personnel compartment, as seen here. Later machines had two drain holes with plugs in the lower front of the hull. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

A cross-section of an early production machine is sketched here. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The older style auxiliary generator and engine access door has been replaced by a flat plate. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75 belonging to the US Army Armor and Cavalry Collection.

The revised fuel filler cover and taillight mounting can be seen on this example. The mechanism for the rear doors has also been moved outboard of the centered mechanism found in earlier vehicles.

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Armored Infantry Vehicle M75.

Like the taillights, the fire extinguisher external control handle housing protrudes from the hull in this example. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

With the deletion of the auxiliary generator and engine, the access panel behind the main engine exhaust pipe was also replaced by a flat plate. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

An interior view through the open rear doors of a late-production machine is provided here. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The cover for the auxiliary engine is the focus of this image. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The auxiliary engine was a General Motors A-41-1 41in³- (670cm³)-displacement, 14.5-horsepower, single-cylinder, constant speed (3,100rpm), air-cooled, 4-cycle gasoline engine. Bore and stroke were 3.625" and 4" (9.208cm and 10cm), respectively, and its compression ratio was 6.6:1. It weighed 370lb (170kg) dry. The starter-generator was a Delco Products Division A-85-85 28 volt, 300 ampere, type II, direct-current, shunt-wound type with an automatic carbon stack regulator. It had an 8.4 kilowatt output. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The commander was provided with six stationary vision blocks for use when his cupola door was closed. When the machine gun was mounted, the door could only be opened when the weapon was placed in the travel position, which is illustrated in the view above. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

Details of the commander's machine gun mount are shown in this picture. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The large steering control lever pivoted as one unit, and driver's legs were placed between the arms of the control. The driver also had a horn switch just to the right of the right-hand steering lever arm. The large dial in the center of the instrument panel is the speedometer. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The driver's auxiliary generator and engine control panel disappeared with the deletion of that assembly. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The driver's early instrument panel is labeled here. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The driver's late instrument panel is labeled here. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The vehicle commander's seat had a total height adjustment of 16.25" (41.28cm) available by pulling the adjustment lever to the left and raising or lowering the seat. The emergency trip lever allowed the seat to be folded down when not in use. The platform was also adjustable by moving it rearward to disengage the two front detents, engaging the desired front detents, and then locking the rear detent with the labeled detent lever. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

One of the early passenger compartment rear doors is shown here, along with part of the bench seat offered for the infantry. The labeled door latch handles were used to turn the cams for the outside door latches that hold the doors open when engaged. Three longitudinal seats were provided for passengers; the left and right were fixed, but the center seat was removable to provide access to the fuel tanks under the passenger compartment floor. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

Late-production machines saw the cam system replaced with a simple latch at the outboard edge of the door. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The armament rack installed in the rear of the vehicle could hold eight rifles or carbines, two .30cal machine guns, or a mortar. The rear of the rack provided stowage for a rocket launcher, or a steam condenser case and water chest for a .30cal heavy machine gun. The center bench seat is visible in front of the armament rack. The seat cushion on this bench could be swung up to access stowage inside the base of the seat. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

Two roof doors were provided for the passenger compartment, and these could be locked with 5" or 10" (13cm or 25cm) gaps or in the fully open position. The doors were locked in position by using the detent post. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The roof doors on late-production vehicles could only be locked in the open position. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The personnel compartment floor in early vehicles was composed of nine removable panels. Panels 6 and 7 were bolted down, while the remainder could be lifted using integral fingerholes. Removing each panel granted access to: 1. Fixed fire extinguisher cylinders and control head, left rear hull drain valve and hull drain valve handle (if equipped), lower left portion of the engine's accessory end. 2. Lower central portion of the engine's accessory end. 2 and 3. Vehicle batteries, master relay, right rear hull drain valve, lower right portion of the engine's accessory end. 4 and 5. Stowage space. 6. Rear fire extinguisher discharge nozzle, left fuel tank, fuel tank shutoff valve, fuel pump cover assembly. 7. Right fuel tank, fuel tank shutoff valve, fuel tank cover assembly. 8 and 9. Stowage compartments. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The personnel compartment floor in late vehicles was composed of eight removable panels. Panels 1, 2, 7, and 8 were finger-lift panels, while the rest were bolted down. Removing each panel granted access to: 1. Forward fixed fire extinguisher cylinder and control head. 2. Storage batteries. 3, 4, 5, and 6. Fuel tank, with the fuel tank cover assembly under panel 5. 7. Stowage space, and the rear fixed fire extinguisher cylinder and the rear discharge nozzle. 8. Stowage space. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The M75's engine and transmission are pictured here. The engine had overhead valves actuated by a single overhead camshaft for each cylinder bank. A single Stromberg float-type double-venturi downdraft carburetor was mounted. Bore and stroke were both 5.75" (14.6cm), its compression ratio was 6.5:1, and the engine could hold 12 gallons (45L) of oil. Dry weight with the flywheel and all accessories was 1856lb (841.2kg). Including the flywheel assembly, length was 49.24" (125.1cm), width was 50.72" (128.8cm), and height was 36.96" (93.88cm). Starting with engine serial number 146, magnetos with internal oilers and steel cams replaced the previous magnetos with external oilers and Buna cams. Engine serial number 219 began the use of a shorter flexible line that connected the vacuum heat control to the cylinder number 5 intake manifold section instead of to the carburetor. Engine serial number 457 was the first to use an oil pressure regulating valve in the engine hydraulic governor system. A 148°F (64.4°C) oil cooler thermostatic bypass valve replaced the previous 185°F (85.0°C) model beginning with engine number 1273. Engine serial number 1531 saw the introduction of new primer filters. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The engine and transmission are seen from the front in this picture. The transmission weighed 1,945lb (882.3kg), was 34.15625" (86.75688cm) long, 33.5" (85.1cm) tall, and 44.75" (113.7cm) wide. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The accessory end of the engine is seen here from the passenger compartment after its access panels have been removed. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The hull front doors have been opened on this early machine, showing an interior view of the installed engine and transmission. The numbers refer to steps in the powerplant removal process. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The same view is provided with a late vehicle. A. Exhaust tail pipe elbow. B. Muffler cover. C. Air duct. D. Cable harness. E. Transmission oil filler cap. F. Transmission oil cooler. G. Throttle control linkage. H. Steering and shifting control linkage. J. Service brake linkage. K. Universal joint. L. Speedometer drive shaft. M. Ground strap. N. Engine jackshaft. P. Transmission. Q. Sump oil filter. R. Brake apply cross shaft. S. Companion flange. T. Cross drive output clamp. U. Starter cable disconnect. V. Engine oil cooler. W. Cable harness bracket. X. Starter relay. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The engine and transmission have been removed from this early vehicle. Note the torsion bar housings cast into the hull. A. Companion flange. B. Power plant electrical disconnects. C. Tachometer drive shaft. D. Fire extinguisher cylinders. E. Main fuel line disconnect. F. Primer pump fuel line disconnect. G. Fire extinguisher dual pull control. H. Accelerator pedal crank. J. Steering and shifting disconnects. K. Brake pedal crank. L. Engine front mounting support. M. Engine jack clevis. N. Engine jackshaft. P. Engine frame rollers and brackets. Q. Engine rear mounting supports. R. Engine oil drain plug cover. S. Transmission oil drain plug covers. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The same view into a late-production machine reveals that the torsion bar housings were eliminated. A. Floor. B. Extinguisher discharge line. C. Extinguisher cylinder. D. Primer pump fuel line disconnect. E. Extinguisher control cables. F. Primer pump. G. Shifting and steering control linkage. H. Companion flange. J. Engine frame roller and bracket. K. Engine jackshaft. L. Transmission oil drain openings. M. Torsion bars. N. Engine oil drain opening. P. Engine mounting support. Q. Fuel supply line disconnect. R. Torsion bar anchor. S. Cable harness disconnect. T. Batteries. U. Fuel tank. V. Tachometer drive shaft. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

The suspension of an early-production machine is labeled. Note the four shock absorbers as well as the reversed orientation of the rear road wheel swing arm compared to that found on the preceding wheel stations. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

The changes made to the late-production suspension can be gleaned from a comparison with the above image. The central shock absorbers were deleted, and the volute bumper springs for the inner wheels were replaced with fixed steel stops, which are hidden by the road wheels. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75.

Track tension was increased or decreased by adjusting the inner compensating arm, and the rear compensating idler was able to keep the track sufficiently tensioned while navigating terrain. Movement of the rear road wheel arm was transmitted to the inner compensating arm via the compensating link. When the rear road wheel passed over an obstacle, the upward movement of its arm swung the idler to the rear, keeping the track tensioned. As the rear road wheel arm returned to its rest position, the idler was brought forward again. (Picture from TM 9-755B Full-Track Armored Infantry Vehicle T18E1.)

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Armored Infantry Vehicle M75.

A late-production idler wheel compensating assembly is shown here. Note the small steel road wheel arm stop behind the intermediate road wheel instead of the earlier volute spring. (Picture from TM 9-7418 Armored Full Tracked Personnel Carrier M75.)

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Armored Infantry Vehicle M75 at the Jackson Barracks, Louisiana.

This is a later-production M75. The access door to the right of the engine, in the sloping plate just behind the engine exhaust pipe, is flat. On earlier vehicles an auxiliary generator was included, and its engine was installed under this access panel, giving it a humped cross section. The driver's hatch is visible on the vehicle's front left corner. The hinges for and outline of the left passenger compartment roof door are just visible to the rear of the vehicle. The large engine access door in the hull front is apparent, and its exhaust pipe is protected by an extension to the right headlight cluster brush guard. The grille on the hull left side is for cooling air exhaust, and the small protuberance in front of this exhaust grille is for external activation of the vehicle's fire suppression system. This would have been found in an indentation on earlier machines. (Picture courtesy Vincent Scorsone.)

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Armored Infantry Vehicle M75 and Armored Personnel Carrier M59 belonging to the US Army Armor and Cavalry Collection.

An interesting comparison between the outgoing M75 and its replacement can be made here. Note the different side access hatch compared to the early machines, and the absence of shock absorbers on wheels two and four.

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Last updated 7 Aug 2021.
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