The two-speed axles are used on some heavy commercial vehicles in order to enable the driver to double the number of gear ratios in the gearbox at his will. generally, the change from one gear ratio to another is made by the driver either manually or by electrical control. Air pressure and vacuum axle shift control are also used.
The figure shows the sectioned view of the two-speed rear axle of a truck manufactured by M/s. Hindustan Motors. It incorporates a hypoid gear and pinion with an epicyclic secondary reduction gear mounted between the hypoid gear and the differential. A ratio change is made by an external shift unit operated by remote control on the gear shift lever.


The axle housing embodies a differential carrier and pinion housing bolted to a banjo-type axle housing with bored extensions accommodating pressed-in tubes located by dowels. The outer ends of the tubes carry the hub bearings. The hypoid gear is bolted to the differential and planet support casing which is mounted on two taper roller bearings secured in the differential carrier by dowelled and bolted caps. Integral pads on the left-hand side bearing cap contact the axle housing to prevent cap deflection under heavy loading. Circular threaded adjusting nuts, in contact with the bearing outer races, are used to position the gear transversely for meshing with the pinion. A four-pinion differential is used and thrust washers are assembled to the pinion and side gears.

A thrust screw in the left-hand side of the differential controls deflection of the hypoid gear under heavy load condition. The pinion is straddle-mounted between a single row roller bearing at its spigot end and a double row taper roller bearing at its outer end. A spacer is interposed between inner races of the outer bearing to control pre-load, and shims are fitted behind the outer bearing for adjustment of the pinion position relative to the hypoid gear. A detachable cover with a single gasket retains the pinion and bearing in the housing. An oil seal installed in the cover contacts a land on the pinion flange. The differential and planet support the case and cover carrying the bolted hypoid gear houses the reduction gear and differential assembly. The planet support case has internal teeth engaged with four bushed planet gears mounted on journals integral with the differential and planet support. These gears are also in constant mesh with a sun gear which has an externally splined sleeve carrying a movable shifter sleeve. The outer end of sun gear sleeve is supported by an anchor, bolted at one end to the adjacent side bearing cap and located in a square holed bush at the outer end. Dovetail shaped teeth on each side of the shifter sleeve engage teeth on the spigot end of the differential and planet support case, or teeth on the anchor when the sleeve is operated. A yoke engaged with the sleeve is splined to a shifter shaft the outer end of which has a keyed lever operated by an externally mounted shift unit. The epicyclic reduction gear and differential gears are lubricated from an oil trough bolted to the right-hand side bearing cap. A baffle in the right-hand side bearing adjusting nut directs oil from the trough to the gears.

Watch the animation video of the two-speed axle with planetary differential:

Next Post »