I am having problems with my speedometer/cable on my 56 F 100, 312, 57 car fordomatic. I have replaced the speedo head with a repro, installed a new cable and gear.  The mech says he doesn't believe the cable gear and the trans gear are meshing.  The trans gear is on solid and not slipping.  Dopes anyone have any idea of what the problem is?


Many thanks,
Larry

Eliminate the transmission and drive gear from the equation.  Turn the cable with a drill and verify that the speedo works.  If yes, it's not the speedo or cable.  If no, then it is the speedo or cable.  If the speedo and cable work, maybe the gear on the cable is incorrect or the gear within the transmission is bad or missing or out of position, if that is even possible.


Lawrenceville, GA

Are You sure the Transmission is a '57? The Cable and Gear changed in 57 to the Cable with clip to hold the Gear on. Earlier style Fordomatic had the Gear just sitting on the end of the Cable. I would think the Drive Gear on the Output Shaft of the Transmission would be different on a 56 and 57 Transmission. Try the suggested Test with Drill and confirm that Cable and Speedo work. If the Drive Gear on Transmission is wrong for your Cable and Gear it can be changed by removing Tail Shaft Housing. Is there still an ID Tag riveted to side of Transmission?

  

I believe oldcarmark is correct  - the rear end of the cable changed in 57. If indeed you have a 57 FOM and you are attempting to use your 56 cable, simply purchase a 57 cable and gear of the correct tooth count. The speedo end should fit your 56 speedometer. I ran a 54 overdrive trans in my 64 for several years and did the opposite to make the speedo function. I purchased a pre 57 cable and gear for my 64 F100  and the speedo worked fine, once I got the tooth count figured out.  Hope this helps, JEFF...................


64F100 57FAIRLANE500

57+ Cables will fit the Speedo Head no Problem. The Cable type does need to Match the Transmission Year as in prior to 57 or 57 and Later. The Bottom end of Cable changed and so did the Gears.

  

When testing the speedometer and cable with a drill, be sure to run the drill in reverse.

John - "The Hoosier Hurricane"

Some Mustang cables will work with both speedo and trans.  Mustang's had two different speedo heads so be careful on the one you get.  They come in different lengths.  A good place to look them up is ebay..
As far as the teeth, there are two orientations so be sure you get the correct one.


54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

I thank you'all for your prompt replies.
1  Based on the trans tag ( PBA-7003-b ), the trans is a 57 car type.
2  The speedo  head works and is a new repro
3  The speedo cable is new and works (must check to see if teeth are angled correctly), and has the correct 57 and up fittings
4  The mainshaft gear is installed correctly, but who knows if it is correct.
     Does anyone know the correct part no and no of teeth??

The mech seems to think that cable gear is to small dia
Again, thanks for your replies,
Larry

If its the Driven Gear on the end of Cable that you want # for its based on Rear Axle Ratio. Not sure what is meant by too small for Cable? The Cable that You are using has the Driven Gear held on with a Clip? Correct? 57 was the first Year for that Type Cable and Gears are not the same as prior Years.

  

In my limited encounters with speedo cables, the driven (cable end) gears used in 57 and up cars were all the same diameter. 



54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ