Due to the difference in the size of the tires used on the 1930 cars, it was necessary to change the speedometer pinion or driven gear by adding an additional tooth to the gear. For example the standard ratio driven gear now has 19 teeth instead of 18 teeth (see Fig. 835).
The new pinion and cap will be serviced only as a unit under partA-17270-D for the standard ratio axle and A-17270-E for the special low speed axle. In other words the pinion and cap will not be serviced separately.
While it is true that the installation of the new gears in a 1928-29 car will cause the speedometer to read a trifle less than the actual speed of the car, nevertheless the difference will be so slight that it would not warrant carrying the old style gears in service.