Classic Mustangs List Archive

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Mail From: (email redacted) (email redacted)

In my 69 Mustang I have a 17 teeth speedometer gear being used with a 3:00 to
1 rear axle and P195/75R14 tires. The car says 70 mph when it is doing
approx. 60 mph. Has anyone found what would be the right speedometer gear for
this application or a good formula to figure this out (I found it almost
impossible to count the teeth on the drive gear in the transmission).

Thanks in advance
Alan

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Mail From: Dave (email redacted)

Alan,

I would go to an 19 tooth driven gear, if you are running a 7 tooth drive gear,
this works out to be about an 11% change, which should bring your speed to about
60 or 61mph.
It is tough to count the teeth on the tranny gear, but if you are running a
4-speed, it isn't too tough to get to and change, just make sure you have a new
tailpiece gasket.

You can look at my web page for more info on speedo gears, just click on the tech
tip regarding speedos:

pweb.netcom.com/~dschmi/mustang.html

Dave

(email redacted) wrote:

> In my 69 Mustang I have a 17 teeth speedometer gear being used with a 3:00 to
> 1 rear axle and P195/75R14 tires. The car says 70 mph when it is doing
> approx. 60 mph. Has anyone found what would be the right speedometer gear for
> this application or a good formula to figure this out (I found it almost
> impossible to count the teeth on the drive gear in the transmission).