It depends on the drive gear in the tranny. I think that earlier AODs had a certain tooth gear that made it impossible to correct anything over 3.73. The later trans had a different gear that you could change the driven gear and it would be OK. Some thing about the pitch of the teeth on the drive gear eats up the plastic driven gear after awhile. Not sure which year the change was made. I think some company out there makes an adapter too. I know, not much help. Mike
Assuming your tire height is between 25.5" and 26", a 23-tooth driven gear will only get you to within an 11 or 12% error. Your T5 probably has a 8-tooth (green) drive gear on the output shaft (you can look through the hole for the speedo cable and check), and the 23-tooth gear won't get you much closer than that.
If you change the drive gear to a 7-tooth (yellow) one, the 23-tooth driven gear will get your speedo error down to around 2%.
Since 23-tooth gears get chewed up easily, there is an aftermarket, 6-tooth (black) drive gear that would allow you to use a 19-tooth (pink) driven gear. That would get you just as close.
Assuming your tire height is between 25.5" and 26", a 23-tooth driven gear will only get you to within an 11 or 12% error. Your T5 probably has a 8-tooth (green) drive gear on the output shaft (you can look through the hole for the speedo cable and check), and the 23-tooth gear won't get you much closer than that.
If you change the drive gear to a 7-tooth (yellow) one, the 23-tooth driven gear will get your speedo error down to around 2%.
Since 23-tooth gears get chewed up easily, there is an aftermarket, 6-tooth (black) drive gear that would allow you to use a 19-tooth (pink) driven gear. That would get you just as close.
The only thing is...isn't changing the drive gear in the tail shaft a PITA? When my trans shop rebuilt my T5, the speedo only worked for 33 miles. I pulled the sensor, and the gear on the trans moved back!! I think the clip in there popped off. They told me just pull the trans and they will fix it for free. But I don't want to do that. Can't I split the case in the car?
The AOD's use an output shaft with the teeth machined into the shaft. Sometime in 1990 ford changed the number of teeth on the AOD's output shaft from 7 teeth(1990 and earlier) to 8 teeth(1990 an later). A 23 tooth speedo gear is correct for the 7 tooth output shaft and 4:10 gears, but a 23 tooth gear is only good for 3:73 gears with a 8 tooth output shaft. The output shafts are interchangeable between the years but require total disassembly of the transmission. I have heard of externial gear reducers to correct the ratio but have no idea where to get one. You may want to try a local speedo shop. Dan