Calibrating Speedometer with 4.56:1 gears and Tremec TKO

HotFox

15 Year Member
Jan 5, 2009
1,050
653
164
SE Michigan
Has any done this?
I found that my car has a 7-23 speedo gears in the transmission. I am running a 275-50-15 tire and found by using online calculators that I need a 25 tooth gear. Obviously this is impossible as the largest gear is a 23 tooth which I have and it is still off 8.35%. What are the alterative cheapest routes without pulling the trans apart to change the 7 tooth to a 6 tooth?
This is what I found:

Speedometer Gear, Speedometer Gears, Ford, GM, Dodge 700R4

About ¼ down the page is a ford ratio adaptor which they will custom make any ratio, but will require a screw on cable which they sell below the ratio adaptor. I will also change to a 21 tooth gear as I read somewhere the 23 tooth gear don’t last long as they don’t mesh perfectly and mine already has all the teeth cracked. So with the gear change and the speedometer error that would put me at a required reduction of 17%.

If I go this route this will set me back $150, is there a better way to go about this?:shrug:

Thank you,
Scott:flag: