fordomatic Transmission Different Models

wdurecka

wdurecka

Junior Member
I have a 1956 Ford Fairlane that I recently changed the Fordomatic transmission. I noticed some differences when installing it. I've read online guys referring to light and medium models. The one I put in looks to be a better built setup with larger bolts on rear mount better torque convertor setup. When I tried to install I see the rear yoke will not slide into the transmission - the replacement transmission has more teeth. The id plate on the side has 312 along with the serial number - does this mean I have a 312 transmission? The replacement came out of a 56 also. I have to count the teeth on the spline and yoke to deterime what I looking for a yoke to finish install. Can anyone provide some advice?
 
Your replacement is a 57 or newer transmission.That's why the output shaft has a finer spline and the convertor is different.The 312 doesn't mean anything about engine size.
 
Y-Blockhead said:
Didn't Ford switch to the water cooled Fordo about this time also. You may need to install a cooler?
Click to expand...

Yes. The 56 Ford-o-matic was the last year for the air cooled converter when used with 8 cyl engines. In 57, the converter was completely different and the trans required coolant lines to the cooler located in the bottom of the radiator tank
 
The 57 can be used in place of the earlier air-cooled models by plugging the two cooler line fittings and using the early convertor.In a normally driven cruiser it will be fine.You will,of course, have to change the slip joint on the driveshaft to match the finer spline on the later transmission.The water-cooled FOM came out in cars built after March of 56.
One other thing you must do is swap the tailshaft housing and the speedometer drive gear from the later transmission to the early one.The later ones drive the speedometer in the opposite direction.
 
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You were right speedometer doesn't work now - I have the tailshaft to switch to replacement transmssion - I don't have the speedomter gear do you know what gear I'm looking for?
 
You not only must swap the tailshaft housings,you must swap the speedometer drive gear on the output shaft of the transmission.It's not a difficult job.Remove the tailshaft housing and you will see the drive gear.It's held in place by a snap ring and a ball that sets in a recess in the shaft.Remove the snap ring and slide the gear to the rear,being careful to catch the little ball.The gear may need a little persuasion(small hammer).
You use your original 55/56 plastic driven gear.
 
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