Speedometer Gear

I spoke to a tranny shop yesterday and they said to get it right they would have to put the car on a dyno. He said he would have to make another gear because it was a ford. Where can you buy another gear for the cable. Does the gear come off the end of the cable or does the whole cable need to be replaced?

 

Just us lazy people.

 

Jeff's Bronco Graveyard has the whole selection of gears. Good prices. Ford still has the gears. You may have to have the part number to find them. Do a search on the net, lots of info an part # for this

Take a drive on the interstate. 60 seconds for one mile is 60 mph.

 

That sounds like crazy talk. There is a clip holding the gear on the end of the cable, very easy to replace. I'm pretty sure you can get them at a Ford dealer. TCI lists part numbers, but when I tried to check pricing or add one to my cart it gave me an error, so I'm not sure if they actually carry them or not. Wouldn't hurt to call a speedometer calibration shop or some dealers near you. You need to to know the # of teeth on your current gear, your stock rear gear ratio, stock tire size, and new tire size if you have changed tires. There are lots of gear change calculators on the net if you do a search.

 

Mustangs Unlimited also sells the gears. As does your local Ford Parts dept.

 

Sounds like the second case of a shop trying to "stick it" to the customer I've seen this morning. Find another shop to do business with . Ford's used the same speedo gears on all their cars and trucks from the 50's till they went to electronic speedo's in the 90's.

 

Also one more question, I have seen two different types of gears. One is called the "driven" gear but I'm not sure what the other one is called. Is the "driven" gear the one that I need?

Thanks,
Ford Guy

 

Yes, the driven gear is the one on the cable, the drive gear is the on the shaft.

 

I bought mine at Ford for about $8.

 

Here is the chart with all the part numbers. Take the first 4 digits from the gear needed, add the 17271, then the last digit from the gear needed. Example: If you needed a 16 tooth for a manual, the part number would be: C0DZ17271A

 

There's also a 23 tooth gear you can add to that list. I think this one maybe an aftermarket item though. Mustangs Unlimited is one source for these.

 

I used bmcdaniel's method and i calculated the percent of error to be around 24%. How many teeth do I need to add or subract to have the correct one?

 

I forgot to say that according to the tachometer i was going 50 mph but my speedo said that I was going 62.

-Ford Guy

 

You need a 20 tooth gear. 7 X 3.55 X 807 = 20,054, divide that by 1000 and you get 20.

 

Here is a site I ran across setting up my 72 Grabber... takes most of the guess work out of it.

http://www.428cobrajet.org/speedo-calc.html

I remember there was another calculator I had found that was also useful that included overdrive tranny calculations... will try to find it.