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speedometer gear selection 66 GT

1008 Views 3 Replies 3 Participants Last post by  rex1965
I have read all the speedo posts but much is contradictory. I have a stock 4 speed toploader. The speedo drive gear is 6 or 7 depending on how it is measured. If you count the starting tooth and the ending tooth it is a 7 tooth. If you count only one end as half of the other end because it is not a complete revolution it is a 6 tooth. I have not seen this addressed. Using the calculator factoring in 25.9 OD tires and the stock 3.00 to 1 rear end 7 teeth gives me a 16.8 gear for the cable and 6 teeth gives me a 14.4 tooth gear for the cable. I could have this backwards but you get the picture. The smallest number of teeth listed in the Mustangsunlimited catalog is 16 anyway. Reading the posts in the disparity between the mph numbers is a nightmare. Please clear this up for me. thanks Bobby
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A common practice among manufacturers were to have the speedometers read slightly higher than actual, this made the cars go out of warranty sooner, although probably not illegal, but saved them millions of dollars, this may still be happening today. My 2 cts. In addition, I am not the one to think of this, there has been several tv and news reports on it. Good Luck.
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