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Discussion Starter #1
I have my new third member in and due to the lower gear I'm 10 mph off at 60. I'm pretty sure I remember that I have the yellow driven gear which has 18 teeth. I read somewhere that 1 tooth is good for about a 5 percent change so I ordered a 21 tooth gear for to slow my speedo down by 15 percent. 1/6 is about 16 percent so I should be fairly close I think. Does this sound right?
 

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Discussion Starter #3
I already ordered it and it has shipped. There is a wine or almost purple looking gear, orange or yellow, white, black, tan and red. The 21 tooth red one is definitely red. The orange or in some cases yellow is the 18 tooth one. I might be able to use another red 21 tooth one for the mustang if it does have 21 teeth. It would still be off but closer than the one that I have. For the stang I'll never have an accurate speedometer unless I go to an adjustable electronic set up.

I guess you will need to count the teeth but if it looks orangish it is probably not what I need.
 

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i bought like 4 or 5 while I was at NPD one day. Only to find out I need to change the drive gear in the trans. when im doing 60, my speedo shows im doing 90
 

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Discussion Starter #7
I ran the calculator and it suggested 16 percent. Assuming that the 5 percent per tooth is right I got 3 extra toofs.

Its already here. I'm waiting for my exhaust to cool a bit before I put it on and try it.
 

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Just look at it like this, one tooth on the driven equals 3 mph.
 
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