Oil sealing and drive pinion durability are improved on both single and two-speed axles due to changes in the differential carrier, pinion bearing retainers, and gasket seals. Attaching holes in the retainers are now reamed and fitted with close tolerance bolts to securely hold all parts in place under the severest conditions. The differential carrier has been modified, permitting the pinion bearing outer race to extend slightly beyond the carrier neck. This assures proper contact and seating with the retainer and new thicker cork and rubber sealing gaskets.

Optional Rear Axles

All truck single and two-speed axles offered as options provide the same axle ration selection as offered in 1958.

A limited slip rear axle introduced in mid-1958 as an R.P.O. on 1/2 ton models is again offered in 1959. While the limited slip portion of this axle is serviced the same as the passenger car Positraction unit, the axle itself is a Series 45 Spicer unit and requires entirely new servicing tools and procedures, as shown in the 1959 Truck Shop Manual Supplement.

Two-Speed Rear Axle Shifting Procedure

Recommended shifting procedures for two-speed rear axle are revised to assure positive, smooth ratio changes. The new method helps complete downshifts quickly, eliminating unnecessary lag.

Procedure changes affect two things. First, the note, "DRIVER NEED NOT DECLUCH," has been removed from all Decals. Second, to shift an axle from high to low speed range, the selector lever is moved from "HIGH" to "LOW." Then, holding the accelerator pedal in depressed position, the shift is effected by quickly depressing and releasing the clutch pedal. By releasing the clutch, a complete power break is accomplished, removing load on shifter mechanism. This permits proper tooth meshing to prevent the lag sometimes experienced by the old method of releasing and reapplying the accelerator pedal.

Both vacuum actuated Chevrolet, and electrically actuated Eaton axles are shifted in this manner. Procedures for shifting from low to high range, or split-shifting in either range, have not changed.

Propeller Shaft Bearings

Improved propeller shaft bearings are used on many truck models, but service procedures are not changed. The replacement bearing package states that the bearing is pre-lubricated and does not require further lubrication.

Fig. 5 - Brake Cooling

However, the cavity between the bearing and the additional set of retainers in the bearing support must still be packed with waterproof grease whenever a bearing is replaced.

Brakes

PASSENGER CARS

Standard Brakes

Cooler-operating brakes with greatly reduced fade and pull, and greater durability are the result of a number of fundamental design changes.

Foremost of these changes is an increase of 27 percent in the brake lining area. This is done by widening each of the front brake drums and shows 3/4-inch, and widening each of the rear brake drums and shoes 1/4-inch. In this manner brake lining areas are increased to 199.5 square inches compared to 157 square inches on the 1958 models. The brake drums are widened with all of the increased width projecting into the air stream for better cooling. Contributing further to improved brake drum cooling are the large cut-outs in the disc portion of the wheels. These holes in the disc permit air to circulate over the entire outer surface of the brake drum (Fig. 5).

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