Speedo Calibration? What Drive Gear?

[93tealstang]

I've got 3:73's in the rear and swapped in a white 23 tooth "Jeep" speedo gear in my 90 GT. I know to get the most accurate speedometer reading, I have to change the drive gear. My question is, what tooth do I need for 3:73's to be the most accurate? 6 or 7 tooth?

 

[89CopCoupe]

AOD or 5spd

7 tooth ...

 

[jrichker]

The stock range of speedo gears work correctly with a limited range of tire sizes.

See http://www.corral.net/tech/gearcalc.html for more help

Check to see if there is a speedometer shop in your area. If there is, ask about the Stewart-Warner speedometer gearbox. I believe it is either a 777 Series Drive Joint Kits and Parts or 666 Series Drive Joint Kits and Parts. It is a small gear box that fits between the speedo pickup gear on the transmission and the speedometer. It has quick change gears that allow you to choose almost any tire size and rear end gear ratio you want. This will allow you to get the accuracy with within 1%-3%. The drawback is that it isn't cheap.
Please excuse the typo (their's, not mine) in the following picture - it should read Custom ratio adapters, not Custom radio adapters.

See http://www.gaugeguys.com/ratioadapt.htm for more info.

 

[MrKwik]

Anybody know what driven gear you need for 3.73's and a C4?

 

[93tealstang]

I've got a 5-speed. I've always read that 6 tooth is the all around best gear, just wanted some confirmation.

 

[89CopCoupe]

I've got a 5-speed. I've always read that 6 tooth is the all around best gear, just wanted some confirmation.

http://www.ffcobra.com/FAQ/speedo.html

http://secure.50resto.com/product1.cfm?SID=1&Product_ID=226&Category_ID=145