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ing gears, and is a form where depreciation of the shifting yokes may result in the gears grating even when in neutral position.
In those forms of gear boxes where the ends of the shafts are supported by single row ball bearings with no special provision for end thrust, noisy action may result in a very short time due to misalignment of the ball bearings at the end of the shaft. Whenever the shifting members are moved to change a gear a pressure of from 75 to 100 pounds is exerted through the shifting yokes on
the sliding gear members, and if these do not engage promptly this pressure becomes an end thrust in the ball bearing. It is only when these are new and practically unused that this pressure can be resisted without pushing one of the ball races a trifle out of line with the other. As soon as the wear in a radial ball bearing amounts to a few thousandths of an inch, which does not appreciably affect the radial capacity of the bearing, the balls can yield to end thrust or lateral pressure to a certain extent and an endwise movement of the shaft results whenever an end thrust is
applied due to poor engagement of the shifting gears. It is not only the pressure from the gear lever that must be taken into account, but the endwise shocks received in changing from a lower to a high gear also. assist in producing depreciation at the bearing. The theoretically correct parallelism of the main and counter shaft is eventually lost if a suitable allowance in the dimensions of the different ball bearings does not serve to equalize the wear due to radial load in the ball bearings at both ends of each shaft. As the gear tooth pressure is highest at the ends where it is transmitted with a large speed reduction to the low gear, this point applies specially to commercial vehicles in which the low gear is used more than in pleasure car service.
Where the use of special end thrust bearings is considered too expensive, adjustable hardened end thrust.sustaining members, such as shown at Figs. 335 and 338, may be used at the ends of the countershaft. Owing to the lack of solidity of aluminum gear box castings, it is usually the plan in constructions of good design, such as at Figs. 332, 334 and 336, to mount the bearings in flange steel or bronze housings in order to enlarge the areas over which the bearing pressures are transmitted to the soft aluminum. Noisy gear box action is sometimes produced due to thin gear box walls which possess sound magnifying qualities, and this feature alone may multiply the volume of noise that would normally be caused by the gear action three or four times, especially if the bearings are located in such a way as to set the gear box in vibration when worn. The only way noise can be reduced is by keeping the ball bearings in proper condition and filling the gearset with a viscous lubricant, such as pure mineral grease, which will provide a cushioning effect against the vibration produced by roughness in either gears or bearings.
FAULTS IN CHASSIS COMPONENTS
Chassis Types—Dismantling a Chassis_Straightening a Bent Frame—Truss.
ing a Weak Frame-Repairing Cracked Side Member—Care and Repair of Springs and Spring Parts—Compensating for Steering Gear Deterioration-Drag Link and Tie-Bar Repairs—Testing Wheel Alignment-Radius Rods, Torque Members and Control Linkage-Universal Joint Forms and Troubles--Front Wheel Adjustment—Muffler Faults—Chassis Lubrication -Locating Acetylene Gas Leak.
Even after the power plant and gearset have received attention, there are numerous points about the chassis of the car that should be inspected if a thorough overhauling is called for. The chassis of any well built car will need but very little attention if the various parts are well oiled until it has been used from ten to fifteen thousand miles. After this distance has been covered, the motorists will probably be annoyed by a series of squeaks and rattles, even though the engine and gearset are in perfect running condition. These rattling noises indicate wear at a number of relatively unimportant bearing points, and even though the depreciation is slight, the looseness at the multiplicity of small joints will produce a noise that will be unmistakable whenever the car is operated on other than perfectly smooth highways. Among some of the things to be looked for are wear in the various control linkage members, sagging or bent frame side members, loose cross members or gusset plates, due to rivets having loosened up in service; stiff action of the springs, due to rust accumulating between the leaves; looseness in the steering gear and steering connections, lack of alignment of the front and rear wheels, looseness of the wheel hub bearings, and numerous other conditions that will be enumerated and discussed in this and the following chapter.