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The identification of the Fordomatic transmission can be rather confusing. There are fifty eight configurations of the Fordomatic transmission built between 1951 and 1959 that could be adapted for use in the 1955 thru 1957 Thunderbirds. In most cases modifications are required, the shifter lever (P/N 7A256) must be changed and in some cases the kick down lever must also be replaced. The output shaft extension housing should be 16 3/4" long.
The 1955/56/57 Thunderbird automatic transmissions had two different extension housings. The 1955 and 1956 models shared the same housing for the air cooled as well as the water cooled transmission. The 1955/56 type is pictured on the right. The hole for the speedometer cable housing and gear angles down into the housing on the 1955/56 models. The 1957 model is pictured on the left. The hole for the speedometer cable housing and gear angles up into the housing on the 1957 models.
The identification tag just aft of the shifter lever reveals the application for the transmission. If the tag is missing these letters are some time cast into the transmission case.The following identifications letters apply to the thunderbirds:
The first Cruise-o-matic (C/M) 3 three speed dual range transmissions were built in 1958. During 1958/59 their were twelve different applications of the C/M transmission. Most if not all can be adapted to the 55-57 Thunderbirds. The shifter lever must be correct, the output shaft housing must be the correct length and the bolt pattern to the bell housing must be as follows. Top holes 8" from center to center, bottom holes 11" center to center and bottom to top 5 5/8" center to center.
In 1960, 61, 62 the C/M transmission was not available. The following transmissions were available FM, FM 2, FX light duty, MX heavy duty. Most of which could be adapted to the 1955-57 Thundebirds.
In 1963 the C/M reappeared in the 1963 Thunderbirds it had a vacuum modulator to promote a smoother shift. 1963 was the last year the C/M transmissions were used. The following is a list of C/M transmissions I.D. number by year:
The following C/M transmissions can be found in trucks:
Some of the C/M transmissions are easy to convert by changing the shifter lever, look for the correct bell housing bolt pattern and output shaft length. In addition to the C/M transmissions their are several other automatic transmission that can be adapted including the FMX and C4.