Speedometer drive gear changes

[MarkH]

Seems my speedometer is running 5mph fast at 50mph. I see in the parts book that there's a variety of speedometer gears in "one tooth" increments.
Anyone got any input on what the mph change would be going up or down 1 or 2 teeth on the drive gear?

[G.B. (All Vinyl Dragon)]

You need to tell What KF Willy’s You have ? 
Correct Tire Size for Your Vehicle? What are You Using to Check Your Speed Standard GPS ?

[MarkH]

You need to tell What KF Willy’s You have ? 
Correct Tire Size ?What are You Using for Your Speed Standard GPS ?

'54 Willys Aero
180HR 15 radial
Garmin GPS that has pretty much matched speedometer speed in any modern vehicle I've used it in.

[rialto]

Most of those old speedometers read slightly fast when new. There is probably nothing wrong with it. They were made that way.

[kaiserkid]

If it is like my Muncie trans in my GTO, changing the tooth count by 1, the MPH changes by 5 MPH. The gear in a Muncie 4 speed is about 3/4" in diameter. If the gear is in a turbo 350 or 400 trans, you need to change about 8 or 9 teeth for 5 MPH. That gear is about 1 1/2" in diameter. Hope that helps.

[kaiserfrazerlibrary]

I agree with rialto.  If you can find one and the speed limit allows it, drive on a measured mile with another person either running a stop watch or regular watch that can show seconds and do it that way.   I have never owned a K-F product in my 45 years with them that was spot on;  usually they are off 5-10 mph on the high side at 60 mph so I would say yours is pretty good especially if it's the original spedo head.

[G.B. (All Vinyl Dragon)]

kaiserfrazerlibrary, New Mexico or Arizona had 2 Sets of Mile Markers to Do Speedometer Check . Then said Strictly Enforced .

Now You can Use GPS & Check. Easy !

[MarkH]

The gear is about 3/4in & has 18 teeth  & a check showed 19 & 20 tooth gears available, as well as the  smaller ones.

Driving around today with the  GPS fully charged showed the speedometer pretty much dead on at slower speeds, only diverging from the GPS as road speed increased. Changing gears will likely just move the "sweet spot" up or down to where it's dead on but not work for the whole range. Seems this will just be another quirk to get used to.

Once again, all good info......thanks for the input!