TM 9-1829A, April 1944
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2021-07-07
Chapter 3: AC division of general motors speedometers and tachometers
5. Description
The following disassembled view of an “AC” speedometer (fig. 15) is typical of these units. Minor variations in
details will be encountered, such as: two types of jewel brackets which are not interchangeable, except when a
matching speed cup is also used; or two types of magnet and first gear drive which are not interchangeable, except
when a matching main frame is also used. Further, some speedometers are supplied without reset-type odometers,
known as tripless types. Some units are equipped with solid reset shafts, while others use flexible reset shafts.
“AC” speedometers and tachometers are furnished for two styles of cable drive. One type must be driven with a
cable tip having a female square, the other having a male square. The female square drive is used with main frames
having casing connector threads
7
/
8
in.-18. The male square drive is used with main frames having casing
connector threads
5
/
8
in.-18. For complete description, operation, and test procedure, refer to paragraphs 2 and 4.
Figure 15: AC speedometer disassembled