Fig. 331.-View of Jeffery Transmission with Cover Plate Removed at Top, Common Causes of Poor Gear Shifting Outlined in Lower Illustration.

nection that on most of the modern cars having clutches of such construction that spinning may result, clutch brakes are provided. As these are used constantly the friction pad, which is often a

limited area, may wear, in which case renewal is necessary to restore the clutch to efficiency.

Fortunately, most gear boxes are built in such a way that the interior may be readily examined. An example of a large opening provided in a gear box by removing a cover plate is shown at the top of Fig. 331. This is the gearset used on the Jeffery fourcylinder cars. The construction of the various gears as well as the selective members is clearly shown. The control levers are attached to the transmission cover plate, as indicated, but may be readily removed with the cover by taking out the bolts holding that member in place and uncoupling the emergency brake actuating rod. The · speed selector, which is actuated by the gear shift lever, fits into suitable depressions in the sliding gear shift rod.

In some transmissions of the sliding gear type the high speed or direct drive is obtained by the sliding gear which provides the intermediate speed having a suitable extension from its face designed to mesh with an internal gear and thus form a positive driving clutch to couple the gearset main shaft portions together. When the teeth on the male clutch member become worn considerable trouble will be experienced in securing positive engagement, and if the wear is such that the width of the teeth is materially reduced a new member will be needed. If the teeth are not worn, but are only burred over at the edges, they may be dressed to proper contour by using a very small, high speed emery wheel on the end of a flexible shaft or by removing the offending member and grinding it in any suitable machine.

Some garage mechanics will anneal a gear in order to soften it sufficiently so that the rough piece may be smoothed with a file. Attempts are afterward made to harden the gear and seldom do these result successfully. In modern gear boxes chrome and nickel alloy steels are used which demand careful heat treatment in order to secure the best quality of steel. These have been carefully developed by scientific laboratory tests and heat treatments are seldom duplicated with the equipment available in the ordinary repair shop. The repairman should not anneal gears unless he is confident that he can treat them properly in rehardening. This means that the nature of the stock as regards its chemical com

position must be known and that the best quenching point for that particular alloy must also be determined. The use of a small, high speed emery wheel will make it possible for the mechanic to dress the gear without softening it or altering its nature, as an emery wheel will cut hardened steel very easily.

Whenever an old gear is removed and is to be replaced by a new one, it is well to make a rough sketch of the gear you desire, indicating the number of teeth, the pitch, the width, the diameter of the gear and the size of the hole going through it. This insures the receipt of a gear that will fit the defective gearbox, and not one for a later or earlier model car of the same make as that worked on. When the cover is off of the gearbox, as shown at the top of Fig. 331, it is possible to test the amount of wear between the shifting yokes and the portion of the sliding gear members on which they fit. On some selective gearsets there is not much space allowed between the gear teeth, and if the shifting yoke wears it may be possible for the shifting gears to rub against one of the fixed gears on the counter shaft and produce noise. The main and countershaft bearings may also be inspected and tested for looseness by grasping the shaft firmly and attempting to move them up and down or from side to side.

If the various components of the gearset are found defective the gear box must be taken apart and given a thorough overhauling. The means of accomplishing this depends entirely upon the design of the change-speed gearing. In those cars where the gearset is mounted under the floor boards as a separate unit, the entire gearbox may be removed without disturbing the power plant or clutch assembly. Gearboxes of this form are usually of the horizontally divided type, and when the top half of the gearbox is removed the various gears and shafts, as well as speed selecting members, are exposed as shown at Fig. 332, A. The first step is to remove the shifting members which are shown shaded at A, this leaving the main shaft and countershaft in place as shown at B. The next operation is to lift the main shaft out, which leaves the gear box as shown at C. After the primary shaft is removed only the countershaft assembly and the reverse stud gear are left in mesh, as shown at D. Lifting the countershaft out leaves only the bottom.

Fig. 332.-Showing Steps in Dismantling Locomobile Four Speed

Transmission.

half of the gearset with the reverse stud gear in place, as indicated at E. To reassemble the gearset the reverse process to taking it apart is followed. First the countershaft assembly, which includes

the gears, the shaft to which they are keyed, and the supporting bearings and their housing, is replaced in position. Next the primary shaft member is put in, then the main shaft, and lastly the control members or shifting rods, until the gearbox is again as shown at A, and ready for bolting the top part in place.

The bearings used on the ends of the countershaft are often of the ball form, as shown at Fig. 333. Different methods of re

Fig. 333.-Conventional Methods of Retaining Ball Bearing Inner Races on Sliding Gearset Countershaft.

taining the bearing in place are followed. That at A shows the use of a cap screw and clamping washer. At B a clamp nut is used to press the bearing inner race firmly against the shoulder. on the shaft, while a lock nut keeps the clamp nut in place. A very simple method, and one that is entirely satisfactory, is shown at C. This consists of grooving the end of the shaft circumferentially and putting in a split ring, as shown at C. A common method of retaining the bearing inner race, and one recommended by ball bearing manufacturers, is shown at D. After the clamp nut is brought tightly against the face of the inner race a locking