Speedometer cable on FMX

Hey guys 

anyone ever replaced their speedo cable ? 

I have FMX  :chin:

I'm confused with the parts needed -- driven gear etc.

Yes, but I have an AOD and I'm pretty sure it's a bit longer than it should be (60-inch, I believe).

Hey guys 

anyone ever replaced their speedo cable ? 

I have FMX  :chin:

I'm confused with the parts needed -- driven gear etc.

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When your speedometer shows the correct speed now, you don't have to mind about the gear, you can use the old one with the new cable.

If you want to change the cable, it has a total length of 150 cm or roughly 5 ft.

If your car was first running in California (maybe also in some other states), the cable has two sections, a short part directly after the speedometer, being attached to a speed sensor which influences your ignition system and a larger section from this speed sensor down to the FMX.

Hope this will be helpful.

Cheers

Frank

The little plastic gear has disintegrated :-/ which is why I'm not getting any speedo reading, so now trying to figure out what it was. 18 tooth - 21 or other

What is your rear axle gear ratio?  Mine are 3.00:1, so I have a 19-tooth speedo gear.  Hope that helps!

The little plastic gear has disintegrated :-/ which is why I'm not getting any speedo reading, so now trying to figure out what it was. 18 tooth - 21 or other

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https://www.tciauto.com/speedometer-gear-calculator

This website can give you enough info to calculate what you need. I believe most FMX transmissions had 8 drive teeth machined into the output shaft, but you will want to check it.

You can order driven gears at Summit Racing. Not terribly cheap at $20 apiece...

https://www.summitracing.com/search?SortBy=BestKeywordMatch&SortOrder=Ascending&keyword=FMX%20driven%20gear

What is your rear axle gear ratio?  Mine are 3.00:1, so I have a 19-tooth speedo gear.  Hope that helps!

Click to expand...

I'm a 9" with 2.75:1 ... a cruiser basically

The driven gears are color coded. You can get more information in this thread, as well as a speedometer gear calculator:

https://www.7173mustangs.com/thread-speedometer-gears?pid=163384#pid163384

Interestingly enough, that calculator says I need a 16 with my gear ratio... but that's running 25-inch diameter wheels.  I have 26.5-ish diameter wheels, so the 19-tooth works out just about right for mine.

I didn't do any fuzzy math for all that - just pulled the plastic gear out of the FMX when I tore it all apart, and ordered a new one of the same color, which dropped right into the speedometer cable/speed sensor assembly in the AOD.