TM-9-2320-280-10 HMMWV Operator Manual Download
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TM 9-2320-280-10 CAUTION When necessary to temporarily operate transfer case in “H/L" (high lock range) or “L" (low range) when additional traction is needed to prevent wheel slippage, avoid sharp continuous turns. Failure to avoid sharp continuous turns while operating transfer case in locked ranges may cause damage to drivetrain. Immediately after operation in “H/L" (high lock range) or “L" (low range), ensure transfer case is shifted to “H” (high range) to avoid damage to drivetrain. If any noises from drivetrain components are heard, ensure that transfer case range is properly selected. For proper transfer case range selection, refer to table 1-9. If transfer case range selection is peculiar to an unusual operating condition, it will be specified in the applicable paragraph. 2-29. OPERATING ON UNUSUAL TERRAIN a. General Rules. Driving off-road over rough or unusual terrain basically requires using good driving sense. Experience is the best teacher, but there are a few good rules to keep in mind when you are in that kind of driving situation. WARNING Use extreme caution when transporting personnel. Rollover protection is available for the crew area only and is not provided in the troop/cargo area. Although certain design characteristics of the vehicle, such as vehicle width, ground clearance, independent suspension, etc., provide improved capabilities, accidents can still happen. Operators are reminded to observe basic safe driving techniques/skills when operating the vehicle, especially when transporting personnel. Vehicle speed must be reduced consistent with weather and road/terrain conditions. Obstacles such as stumps and boulders must be avoided. Failure to use basic safe driving techniques/skills may result in injury or death to personnel and damage to equipment. (1) Use “H/L” (high lock range) or “L” (low range) only when absolutely required by the conditions identified in table 1-9. After operations on unusual terrain, be sure to shift the transfer case from “H/L" (high lock range) or "L" (low range) to “H”(high range) to avoid damaging drivetrain components. (2) Select proper transmission and transfer case driving ranges. Refer to table 1-7 or table 1-8 for transmission range selections. For transfer case range selections, refer to table 1-9. (3) Keep engine at a moderate speed. The engine works at its best pace in the mid-range revolutions per minute (rpms). You can slow down or speed up quickly without changing gears if you get into a tight spot. Use the transmission shift lever and transfer case shift lever to control the engine speed. (4) Attempt to keep wheels from spinning. If the wheels start to spin, ease off the accelerator pedal until the wheels regain traction. (5) The instructions for placing vehicle in motion (para. 2-11) also apply to operating on unusual terrain. 2-138