Fordomatic: Are there different output shafts for different Fordomatics?
 

Do different Fordomatics have different output shafts with a different number of teeth or size? For example, would the output shaft from a truck have a different number of teeth than a Thunderbird?

I have been working on repairing (not restoring) a 1956 T-bird for nearly 5 years and have run into many problems caused by previous owners installing non-T-bird parts such as a 239 engine and a Fordomatic from either a passenger car or truck (or possibly some combination of both). I replaced the transmission with a T-bird tranny only to find the torque converter did not match (wrong number of teeth) and had to replace the turbine in the converter. Now I’m ready to install the drive shaft and the yoke is not easily sliding over the output shaft and I’m wondering if I have another problem with a mismatch of teeth.

Re: Fordomatic: Are there different output shafts for different Fordomatics?
 

Never mind. I took another run at it and got the drive shaft installed.

Re: Fordomatic: Are there different output shafts for different Fordomatics?
 

From info I'm finding (parts book & internet) the original slip yoke depended on the engine installation and associated transmission. When the T-bird came out, they used the new medium case transmissions. The medium case came out for heavy duty applications like the 312 T-bird but the 292 also had the medium case PMB-C transmission. There were two PAW (PAW-C & F) and two PME transmissions (PME-B & C) used for 1956. 1957 had different part numbers. Most transmissions are similar but they changed to water cooled in 1956 so that would be a distinct difference between 1955 & early 56 and late 1956. I think the output shaft splines changed in 1957 to a finer spline with a higher count.
Early ones were likely 16-spline but there was a standard part (P/N B5C-4841-A) that was likely for standard transmissions and a heavy duty part (P/N B6S-4841-A) for 312 engines in T-birds, police cars, and others with the FOM and the overdrive T85 standard shift. The parts book doesn't list the spline count for the 1956 T-bird with FOM.

What is the spline count? Most of the differences between transmissions of the same basic type would have been for mounting and tail shaft length with consideration for speedometer gearing. Otherwise they are pretty much the same. If the spline count & diameter is a match then it may just be that the air gets trapped during installation and makes it hard to go on. Some manufacturers drilled a small hole in the knuckle plug so that it could breath.

Re: Fordomatic: Are there different output shafts for different Fordomatics?
 

Thanks, as you can see from my second post, I got it installed. I did have 16 splines.

Re: Fordomatic: Are there different output shafts for different Fordomatics?
 

in 57 they all went to 27 splines for the output.

Re: Fordomatic: Are there different output shafts for different Fordomatics?
 

Yes. Attached is an MPC application chart for 49/59 cars only -

Re: Fordomatic: Are there different output shafts for different Fordomatics?
 

does anyone know where i can a u joint that will allow me to put a 57 yoke on a 56 driveshaft.i used to hear there was one.

Re: Fordomatic: Are there different output shafts for different Fordomatics?
 

A shop that does drive shafts should be able to change the shaft to accept the other yoke . Or he may have info on a u-joint

Re: Fordomatic: Are there different output shafts for different Fordomatics?
 

Try this - https://www.dennysdriveshaft.com/c13...9_x_3.625.html