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.
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.
The 23 tooth gears aren't usually too bad on the 5 speed cars. The Automatics chew them up pretty good.
You have an 8 tooth drive gear in your '90. To install the 7 tooth gear that came in the Mustang though 1989 you have to take the tailhousing off of the transmission. Once the tailhousing is off the swap is very easy.
You have an 8 tooth drive gear in your '90. To install the 7 tooth gear that came in the Mustang though 1989 you have to take the tailhousing off of the transmission. Once the tailhousing is off the swap is very easy.
Here's an interesting tidbit!
Yes, they get chewed after a few thousand (3-5K) miles BUT they keep working like that for some reason. My 23 toother had half the teeth missing and my speedo was right on with no jumps.
Yeah baby! 4.56's and an auto!! You want gear chewing? Well, I got gear chewing right here.
Yes, they get chewed after a few thousand (3-5K) miles BUT they keep working like that for some reason. My 23 toother had half the teeth missing and my speedo was right on with no jumps.
Yeah baby! 4.56's and an auto!! You want gear chewing? Well, I got gear chewing right here.