Several changes have been made in speedometer parts used in the truck.
The thread pilot diameter of the AA-17269 speedometer driven gear bearing has been changed from 5/8“ to 3⁄4″ to fit the new square end speedometer shaft and the casing assemblies. While the new bearing is 1⁄8”larger in diameter than the old bearing, these bearings can be used interchangeably.
The speedometer shaft has been changed from a round end shaft having a key drive, to a square end shaft.
To correspond with the new shaft, the speedometer driven gear is made with a square hole I(see Fig. 932) instead of a slotted round hole as shown in Fig. 934. This changes the symbol number of the speedometer driven gear used with the low speed axle (6.6 to 1) from AA-17271-FR to AA-17271-G.
On the high speed axle, in addition to changing the gears to accommodate the square end speedometer shaft, the number of teeth on both the drive and driven gears were changed to give a more accurate speedometer reading.
This change was as follows: AA-17285-FR speedometer driving gear. This gear had 6 teeth. (See Fig. 934.) It is replaced by AA-17285-H driving gear having 4 teeth. (See Fig. 933.)
AA-17271-DR speedometer driven gear had 19 teeth. (See Fig. 934.) It is replaced by AA-17271-H having 13 teeth. (See Fig. 933.)
MODEL “A” SPEEDOMETER PARTS
The only change made in the Model “A” speedometer parts was to change the speedometer shaft from a round end to a square end shaft. Also the driven gear shaft in the speedometer gear and cap assembly was changed from a round end shaft having a key drive to a square end shaft.
The symbol numbers of the new assemblies are A-17270-F (3.78-1 ratio) and A-17270-G (4.111-1 ratio). The old design assemblies A-17270-DR and A-17270-ER will be held for repairs.
SCREW A-20216-S6 OBSOLETED
To lessen any possibility of distorting the instrument panel by screwing in the instrument panel to speedometer cable support screw too far, a new screw with shorter threads (A-20221-S6) has been adopted.
The old design screw (A-20216-S6), which was threaded all the way back to the head of the screw, has been obsoleted.