In my 91 AOD i have 3.73's and a 23 tooth gear, it seems to be about 5 mph off at 55mph. (Reads 60mph) I assume that since its a 91 I have a 8 tooth drive gear, since i'm getting my transmission rebuilt, could i switch to a 7 tooth drive gear so my speedometer would be more accurate. I noticed that when I took my tranny out my speedo gear was looking chewed up, I just had it put in maybe 4-5 months ago. The Steeda website says that if i went with the 7 tooth then i could get the 21 tooth purple gear. I just want to get this speedometer accurate and now is a good time to do so with my transmission out. Thanks for the replies.
Speedometer Gear
- Thread starter squeak_cg
- Start date
93 LX
Founding Member
Axle Ratio 6T 7T 8T- Drive gears
Driven gears
2.73 - 16 18
3.08 - 18 20
3.27 16 19 21
3.55 17 20 -
3.73 18 21 -
4.10 20 - -
4.30 21 - -
4.56 - - -
from D&D performance www.ddperformance.com
Driven gears
2.73 - 16 18
3.08 - 18 20
3.27 16 19 21
3.55 17 20 -
3.73 18 21 -
4.10 20 - -
4.30 21 - -
4.56 - - -
from D&D performance www.ddperformance.com
TRWXXA
Member
It's not likely that you will get it exact. My '93 SSP (with AOD) now has a 3.73 rear end. On the stock SSP tires (26" dia.) it would need a 23.2 tooth speedo gear. That's a 0.8% error. Right now, I have 25.6" tires on it, which requires a 23.7 tooth gear, which is a 3.0% error.
23 is as close as you can get (duhhhh). If you want to get the speedo right on, you'll have to adjust the tire size.
Chewed-up 23 tooth gears are normal. The teeth are very thin and break easily. I buy replacements two at a time.
Changing to a 7 tooth drive gear will help, but depending on your tire size, you'll need a 20 or 21 tooth driven gear. You could still see an error as high as 3 percent if you're in between the two sizes.
And don't forget, the speedometer itself could be off a little too, compounding the errors in your indicated speed. I believe speedometers can have an error as high as 5% when leaving the factory. The SSP's "Certified Calibration" speedos had to be within 2 or 3% at all speeds. (I'm sure someone will let me know if my numbers are off.)
On some model years, it's not easy to change the driven gear, because it's machined as part of the tailshaft.
Good luck.
23 is as close as you can get (duhhhh). If you want to get the speedo right on, you'll have to adjust the tire size.
Chewed-up 23 tooth gears are normal. The teeth are very thin and break easily. I buy replacements two at a time.
Changing to a 7 tooth drive gear will help, but depending on your tire size, you'll need a 20 or 21 tooth driven gear. You could still see an error as high as 3 percent if you're in between the two sizes.
And don't forget, the speedometer itself could be off a little too, compounding the errors in your indicated speed. I believe speedometers can have an error as high as 5% when leaving the factory. The SSP's "Certified Calibration" speedos had to be within 2 or 3% at all speeds. (I'm sure someone will let me know if my numbers are off.)
On some model years, it's not easy to change the driven gear, because it's machined as part of the tailshaft.
Good luck.
