TM-9-2320-280-10 HMMWV Operator Manual Download
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TM 9-2320-280-10 Change 1 2-139 b. Unusual Terrain Driving Techniques CAUTION • Do not shift into any lower gear than is necessary to maintain headway. Attempt to maintain a constant engine speed. Over- revving engine will cause the wheels to slip, and traction will be lost. • Before ascending or descending steep hills, stop vehicle, place transmission to “N” (neutral), and shift transfer case to “L” (low range). Failure to shift transfer case to “L” (low range) before ascending or descending steep hills may result in damage to drivetrain. (1) Before climbing a steep hill, shift the transfer case into “L” (low range) and the automatic transmission into “1” (first). If wheels start to slip, “walk” the vehicle the last few remaining feet of a hill by swinging the front wheels sharply left and right if situation permits. This action will provide fresh “bite” into the surface and will usually result in enough traction to complete the climb. CAUTION When “L” (low range) is used for “engine braking” while descending steep grades, avoid sharp continuous turns. Failure to avoid sharp continuous turns while operating transfer case in range may cause damage to drivetrain. (2) You can proceed safely down a steep grade by shifting the transfer case into “L” (low range) and the transmission into “2” (second) or “1” (first). Let the vehicle go slowly down the hill with all four wheels turning against engine compression. WARNING Do not travel diagonally across a hill unless it is absolutely necess- ary, or injury to personnel or damage to equipment may result. (3) When moving across a slope, choose the least angle possible, keep moving, and avoid turning quickly. (4) If it is difficult to shift out of a locked range, drivetrain torque buildup may have occured. If necessary to relieve drivetrain torque buildup when leaving a low traction surface for a high traction surface, the vehicle should be backed up for a distance of approximately 5 ft (1.5 m) before proceeding. 2-30. COLD WEATHER STARTING BELOW +32°F (0°C) WARNING Starting aids will not be used on the engine. Use of starting aids will cause damage to vehicle, injury, or death. (1) Start engine (para. 2-10). WARNING • Do not use the hand throttle as an automatic speed or cruise control. The hand throttle does not automatically disengage when brake is applied, resulting in increased stopping distances and possible hazardous and unsafe operation. • Do not fully apply hand throttle when engine is not under load. NOTE If engine cranks slowly and voltmeter indicates low battery charge level, attempt to slave start vehicle (para. 2-23). If vehicle still will not start, perform troubleshooting procedures in table 3-1.