1957 Ford Fairlane 500

[Randall Hornback]

Hi again Ford Barn Men, i have another question. I have a friend who has a 1957 Ford fairlane 500 390 V/8 Fordomatic. He says it is running about 5 miles fast on speedomeater, he has change the gear on transmission that hooks to speedometer cable it was the 19 thooth gear. He says it has the right size tire size on it. Can some one gives us some help on this, would appreciate it very very much. Thanks a whole lot.

Randall Hornback

 

[dmsfrr]

5 mph fast at 50 miles per hour?
Find a gear for the bottom end of the speedometer cable with 20 or 21 teeth and it should be closer to what he needs. I think each tooth changes by 5%, but it's been a very long time since I did one.

or 5 mph faster all the time?
The speedometer needle is out of position.

 

[Motorhead6]

If the speedometer reads high, put a gear with an extra tooth on it. If it now has 19 teeth, put a 20 tooth gear on it and it will slow the speedometer down. Check it against a GPS. This will slow the speedometer down by about 5% or 3 mph at 60 mph. You cannot get it perfect, just close. You might also try a 21 (9%) tooth gear. They're not expensive at NPD, so buy them both.