SpeedoGear

90 · Mar 14, 2007

i know i should be posting in tech, But i already dont know what im talking about, So talking to Tech support will only make me Feel Stupid'er.. lol

im speedo is off 8 mph.. i have a 3:73 rear end, with 17" rims.. tire size reads as- 275- 40-17.. Who Can Help me.. If no one Please Move this to Tech... i have my speedo still in my car, And another that a buddy gave me.. i went to a ford dealership and he was on some Drugs.. so i shook my head a smiled. i guess i really just need to know how many teeth are supposed to be on that gear.. Thanks for anyhelp..

Love Always
90~!

795.0pacecar · Mar 14, 2007

Need more info. 8mph high or low? It probably has alot to do with the 8 tooth speedo drive gear and the fact you cant correct it when you use 3.73 or higher rear gears.

90 · Mar 14, 2007

795.0pacecar said:
Need more info. 8mph high or low? It probably has alot to do with the 8 tooth speedo drive gear and the fact you cant correct it when you use 3.73 or higher rear gears.

8mph low... sorry about that, i counted the gear i have in my hand it has 17 teeth on it.. i dont know how many the one in my car has i havent pulled it out yet

90 · Mar 14, 2007

theres gotta be Somthing i can do... Why cant i fix it with 3.73's ?

mustangjoe87 · Mar 14, 2007

http://www.steeda.com/products/speedometer_recalibration_gears.php

90 · Mar 14, 2007

well with that link i know its either the RED or the White.. how do i know the differance if its an 8tooth or 7 ? the one in my hand has 17teeth, and its Green.. Glad i didnt just put that in there

mustangjoe87 · Mar 14, 2007

the 7 or 8 tooth is a drive gear in the trans

Matts89Notch · Mar 14, 2007

I'm glad this came up, I'll ask in here if you don't mind instead of starting a new thread.

My speed reads about 3-4 mph too high with the factory wheels and tire size. My car has a crome diff cover so I know it has been messed with but I'm unsure if they are the 2.73's...Maybe a 3.08 or somthing? The gears feel stock and are a lot taller than my friends 4:10 cause I was still winding out 3rd and he was already in 4th gear...Should I rotate the tire to see how many time my driveshaft spins and go from there?

BlooDReigN · Mar 14, 2007

93LX-HOPE2B said:
I'm glad this came up, I'll ask in here if you don't mind instead of starting a new thread.

My speed reads about 3-4 mph too high with the factory wheels and tire size. My car has a crome diff cover so I know it has been messed with but I'm unsure if they are the 2.73's...Maybe a 3.08 or somthing? The gears feel stock and are a lot taller than my friends 4:10 cause I was still winding out 3rd and he was already in 4th gear...Should I rotate the tire to see how many time my driveshaft spins and go from there?

That's about the only way to figure it out, short of pulling stuff in the rear end apart.

87_stang · Mar 14, 2007

Just a quick question on the spinning the wheels/driveshaft thing. How do you do that to tell what gears you got? The guy I just bought my car from said he wasn't sure if it had 3.73's or 4.10's, but thought it was the 3.73's.

DMAN302 · Mar 14, 2007

sorry didn't read the thread, just wanted to say hello....hello

795.0pacecar · Mar 15, 2007

90mustang_GT5.0 said:
well with that link i know its either the RED or the White.. how do i know the differance if its an 8tooth or 7 ? the one in my hand has 17teeth, and its Green.. Glad i didnt just put that in there

The gear in your trans that drives the speedo gear is an 8 tooth gear, in order to correct your speedo you need a 24 tooth gear. Problem is they dont make one because it would just get chewed up anyway, even a 23 tooth white gear will most likely get chewed up and it wont be spot on accurate but it will be closer.

The best thing to do is pull the transmission and change the drive gear.

90 · Mar 15, 2007

795.0pacecar said:
The gear in your trans that drives the speedo gear is an 8 tooth gear, in order to correct your speedo you need a 24 tooth gear. Problem is they dont make one because it would just get chewed up anyway, even a 23 tooth white gear will most likely get chewed up and it wont be spot on accurate but it will be closer.

The best thing to do is pull the transmission and change the drive gear.

i know that i dont know alot about cars (mechanic wise).. But i Shouldn't have to take My tranny out... ill spend the $10.00 and the 10 min This way, If it dont Fix the problem 8Mph under isnt hard to get used too.. it can remain that way

jrichker · Mar 15, 2007

The stock range of speedo gears work correctly with a limited range of tire sizes. The 23 tooth white gear works good for some guys, but self destructs in a few months for others.

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 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.

90 · Mar 15, 2007

thanks jrichker

Matts89Notch · Mar 16, 2007

My friend spun my tire exactly one full turn and my ds went about 1 3/4 turns....i have no idea what this means....

90_Red_LX · Mar 16, 2007

The 23 tooth chews up with me after a period of time, but I'm just going to pop another one in until my clutch comes out. It's still holding good, but the h/c should take care of it.

TRWXXA · Mar 17, 2007

Matts89Notch said:
My friend spun my tire exactly one full turn and my ds went about 1 3/4 turns....i have no idea what this means....

Obviously you mis-counted, or your friend did. Sounds like your friend turned the tire only half way.

Mark the driveshaft with a Sharpie, or piece of tape. Have a friend (who can count) slowly spin the tire 10 times (mark the tire or rim with a piece of tape too) while you count the driveshaft rotations.

If the DS spins 27 times, you have 2.73s. If it spins 30 times, you have 3.08s. 32 or 33 times means 3.27s, 35 or 36 times means 3.55s, etc, etc.

Turning the tire only once is not enough to accurately count the turns of the driveshaft. It's too hard to tell the difference between 2 3/4 turns and 3 1/10 turns, or between 3 1/2 turns and 3 3/4 turns, etc.

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