MIL-T-62735 Trucks And Truck Tractors: Modified Commercial, General Specification ForThis specification covers general requirements for the classes, models and types of modified commercial trucks indicated in the specification title above and in 1.2 below. This specification is intended only as a document to be referenced in detail specification sheets that must, as a minimum, cover detailed truck body requirements and specify the model and class required from table I.

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MIL-T-62735

3.3.8  Cooling system.  The cooling system shall maintain the engine coolant at a temperature below the boiling point.  This shall be accomplished with the vehicle loaded to GVW and GCW and operated at an altitude of 3050 meters (m) (10,000 feet) above sea level or in an ambient air temperature of not less than 52° Celsius (°C) (125 degrees Fahrenheit (°F)). Tilt cabs shall have a radiator servicing access door to permit the coolant level to be checked. When specified (see 6.2), radiator and heater hoses shall be of silicone rubber.

3.3.9  Fan clutch.  The cooling system fan shall have a fan clutch.

3.3.10  Exhaust system.  On class 36 and larger truck tractors, the exhaust shall be

vertical.  Vertical exhausts on truck tractors shall have a heat shield.  On all other types of trucks,

vertical exhausts shall have a heat shield if exhaust components are capable of being reached easily by personnel entering or leaving either side of the cab.  Vertical exhausts shall have a hinged rain cap.  See 3.5.17, 3.9.2.

3.3.11  Transmission.  Unless otherwise specified (see 3.3.11.5), the vehicle shall have a manual transmission.  The input torque capacity of all transmissions shall be at least equal to the maximum torque delivered by the engine.  Gear ratios in the transmission and the axles shall provide a progressive shifting pattern throughout the complete range and shall provide performance as specified in of 3.2.1 through 3.2.4.

3.3.11.1  Manual transmission.  The manual transmission in vehicles up to class 21 shall synchronize shift for at least the three highest forward speeds or, for class 21, may be of the constant mesh type.  All other classes shall provide for maximum ease of shifting in all speeds. When more than five forward speeds are required, a multispeed transmission, auxiliary transmission, two speed axle (4x2 and 6x4 only) or two speed transfer case (4x4, 6x6 and 8x6 only) shall be provided.  Auxiliary transmissions shall have air shift.  The transmission and other gear train and axle equipment shall provide not less than the number of vehicle forward speeds specified in table VII.

TABLE VII.  Vehicle forward speeds and transmission PTO openings.

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