Figure 2-3.-Cross section of a disc clutch.Figure 2-4.-Disc clutch operation.Figure 2-5.-Clutch linkage.2-3transmission transfers engine power from the clutchshaft to the propeller shaft and allows the operator tochange the gear ratio between the engine and the rearwheels.Dual-ratio, or two-speed rear axles are often usedon trucks. They have two gear ratios that can be chosenby the operator, usually by a manual control lever. Adual-ratio rear axle works the same as the auxiliarytransmission; it doubles the number of gear ratios fordriving the vehicle under the various loads and ondifferent roads.The most common transmission type is thesynchromesh transmission. The synchromeshtransmission is basically a constant mesh, collar-shifttransmission with an extra device, called a synchronizer,to equalize the speed of the mating parts before theyengage. The synchronizer is used in all manualautomotive transmissions and is common in otherequipment where shifting while moving is required.Part of the prestart operation is to check the fluidlevel in the manual transmission. The normal level oflubricant is usually at the bottom of the filler plugopening. When lubricant is needed, you should alwayscheck the operator’s manual for the location and type oflubricant required for the transmission. When you keepthe lubricant level correct, the gear teeth are protected,foam is reduced, and the transmission runs smoothly.Some transmission troubles that you may encounterand must document are as follows:llllllHard shiftingSlipping out of gearNo power through the transmissionTransmission noisy when in gearGear clash in shiftingOil leaksManual Shift OperationSkill in manual shifting is a requirement ofprofessional driving. Poor manual shifting results inpoor vehicle performance and can cause vehicledamage. Know the gearshift lever positions so well thatyou can shift to any gear without looking at the shiftlever. The gearshift pattern is usually diagramed in thevehicle or in the operator’s manual. Never move thegearshift lever from one position to another while theengine is running until you have fully depressed the
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