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Discussion Starter · #1 ·
I am getting ready to swap in a set of 4.10 gears into my AOD car and would like keep the speedo pretty acurate. I have noticed that some people use the 23 tooth gear. Does Ford make this gear? Is it Jeep only? Also how close is the speedo with this gear. Any ideas would be very helpful on using this gear or a better way to do it. Thanks Mike BTW this is for my 91 hatch
 

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I wish some one would chime in cuase I got the same prolem i already have 410 in mine and its waaayy off
 

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Discussion Starter · #3 ·
did you change your speedo gear already?
 
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How many teeth are there in the gear of your output shaft? That makes a difference also. Depending on what gear you have there--6 or 7 tooth--you may or may not be able to get your speedo running correctly. There are some sites somewhere I could find them but I'm not on my home pc--that have conversions that will help you find the right gear combo. You can get the 23 tooth gear, if that's the one you need, through some of the aftermarket Mustang parts dealers, like Texas Mustang Parts.
 

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nah i changed it when i went to 355's but when I went to 410's i never saw a gear that was supposed to correct an AOD with 410's
 

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There is only one speedo gear to use it is the 23 tooth white gear. It might not be 100% correct but pretty close. The only other way would be to have your speedometer recalibrated.
 

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90 and later AOD's have an 8 tooth gear on the output shaft. It is machined into the shaft, not changeable. 23 tooth is the max available and it sometimes has a limited life. They do make correction boxes that fit between the trans and cable. They require you to figure the percentage of error and they adjust from there. Do a search on google under ratio correction box. If you rebuild or order another AOD specify a 7 tooth output shaft gear, 1989 and earlier. It gives you a little more correction range.
good luck,
 

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Dallas mustang has a box that will allow you to have correct speedometer readings regarless of what tire size, or rear end gears you run.
 

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Therre is NO gear available that you should even try. The AOD has an 8 tooth gear built into the mainshaft. There is no speedo gear that matches perfectly with the 4.10. I would not suggest tring to change in manually. if you put the wrong gear on it will not mesh properly and the nylon from the gear ends up inside the Valve Body and we know what happens from there.
 

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I believe everything the above is saying. The white gear didn't even last in my 89. So a calibration box would be great if it works. none of gears lasted with my 4 .10,s so I disconnected it with no gear and switched to a total manual valve body that keep loosing my dash bolts. It banged like a bomb! 15 years later I have another aod just stay with 3.73,s it works and is only 5 off at 65-70.
 
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