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Discussion Starter #1
When we pulled my tranny to do the work on it, we took the speedo gear out and it already has a white speedo gear.
Does that mean I already have a upgraded gear? I had the 2.73 axle code. I ordered a set of 3.73's a couple months ago, but never put them in. And I ordered my 23 tooth (white) speedo gear last week. As I got to looking, I noticed it has the same gear I ordered. So how could I find out if I have a different gear? Could it be 3.55, 3.73, or 4.10?
 

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If you have a 5 speed. That gear is for a 3.73 or 4.10 (for both it isn't totally accurate, but close). I'd say, jack up your back end. watch your driveshaft, and spin your tire. Watch how many times your tire spins to one revolution of the driveshaft. If it turns 3 and 3/4 times, then you have a 3.73 ratio. If it turns just over 4 times, you have a 4.10 ratio. Its that simple.
 

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Discussion Starter #3
to me, the car doesn't feel as if it has a gear in it. But my friend drove it, and he think it does have a gear :confused:

I can't turn the driveshaft right now because it is currently laying beside the car while my tranny is in pieces :(

But I was taching 1800-1900 rpms @ 60mph in 5th gear from what I remember (before I installed my white gauges, now my speedo and tach are all screwy!).


How much could I sell my new, still in box 3.73 gears for??
 

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Well, did u buy the car used? If it does have the stock gear in it, the previous owner was cheating with the actual mileage off the car! :eek:
 

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that's not 100% accurate either... my speedo/odo is accurate with my 4.10's because i use my Hypertech Programmer to correct it, and do you think i'd let the programmer stay in the car if i traded it? no way! but the mileage would be accurate, to the point where i returned the stock program to the car...
 

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Discussion Starter #8
so if my speedo was off, it'd throw my odometer off??
I doubt anyone changed the gear in the car, because EVERYTHING else was completely stock! I don't believe someone would only change the gear, and nothing else.
I'm just wondering why I have the white speedo gear. I can't go turn my driveshaft because my tranny is out of the car at the moment.
 

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What size tires/rims do you have?

How much is the tranny work going to set you back?

Generally the gear put in to compensate for 3.73s is a 23 tooth gear. Count 'em.
 

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Discussion Starter #11
when I got the car, it had 255/45/ZR17's all the way around. Then when my alignment started to freak out, I replaced the rear with 245/45's. The front still has the 255/45's. I'm not replacing the front until I finish up installing the suspension work. Then I'll move the 245's up front and get some 275/40's for the rear (probably).

And as far as the tranny work, I dunno yet. A friend is doing all the work for me. So far, all they have found is a broken keyway piece. A little $3 part!! :mad: :mad: But they have yet to get the last set of gears and forks out. So hopefully there is nothing else wrong.
 

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Hopefully you'll be back on the road in no time. Count the # of teeth on the speedo gear.
 

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Discussion Starter #13
Yeah I hope I'm back on the road soon too! It's been 1 week and 2 days without my 'Stang! IT SUCKS! :( :( :(

And the gear appears to be the 23 tooth gear. It looks pretty rough though. Starting to shred apart.
Are their any other white speedo gears?
 

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On a 98 GT which has an 8 tooth speedo drive gear, the white 23 (not a Ford part so fit is not perfect and it doesn't last long) corrects for 3.55 rear. Some people also use it for 3.73's, but that would add about 5% (difference between 3.55's to 3.73's) error to whatever error is there for 3.55's . The 255X45X17 tire actually is a good idea, because even with 3.55's and white 23, there is some error the slightly larger diameter 255's partially take out.

A better way to correct is with a SpeedCal, and the only way to correct for anything over 3.55's.
 

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Ditto everything that Ralph said...

However, since you have the tranny apart anyway you could have the mechanic replace the 8-tooth drive gear with a 7-tooth version (like the cobra T-45's have) which will allow you to correct for the 3.73's with the 23-tooth VSS gear. If you can determine that you actually have 3.73's, this would be the least expensive way to accurately correct your speedo. Anything higher (3.90, 4.10, etc.) and you need to go electronic as mentioned above.

BEGIN EDIT
Due to my first official senior moment (I just turned 40 a couple of weeks ago) I typed 23-tooth instead of 21-tooth. The correct VSS gear is indeed 21-tooth to correct for 3.73's when used with a 7-tooth internal drive gear. END EDIT
 

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BlueStang...I'm sure it was a typo but on a Cobra with 7 tooth speedo drive gear you correct 3.73's with a red 21 (black 20 for 3.55's). The white 23 is used for 4.10's, and wears quickly, which is main reason (accuracy is another) I installed the excellent SpeedCal.
 

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Ralph Greene said:
BlueStang...I'm sure it was a typo but on a Cobra with 7 tooth speedo drive gear you correct 3.73's with a red 21 (black 20 for 3.55's). The white 23 is used for 4.10's, and wears quickly, which is main reason (accuracy is another) I installed the excellent SpeedCal.
Yep... you're right on all counts except one. It wasn't a typo, I actually hit that "3" on purpose... however I was having an acid flashback at the time. ;) 21 is indeed the proper gear to correct for 3.73's with a 7-tooth drive gear.
 

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Discussion Starter #18
Where would I get a new drive gear? I don't know anything about those. I don't even know where it is or what it looks like.

My friend who seems to think I have a gear, believes it's 3.55's. And it was taching around 1800-1900rpms @ 60mph. So that sounds about right.
Is their any way I can figure what gear I have with the tranny and driveshaft out?
 

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You can pick up the internal gear at any Ford dealer and they're not expensive. Your mechanic will know what it is, where it goes, etc., etc.

If your car's on jacks or a lift, get under the car and look towards the back at the rear end and you'll be able to see the area where the driveshaft connects. Have somebody turn one of the rear wheels one full circle while you count how many rotations occur. If there are 3 1/2 rotations, then you've got 3.55's... 3 3/4 rotations then 3.73's and so on. You might want to use chalk or a grease pencil to make a mark to make it easier to count the rotations.
 

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Is there anyway to validate I have a 7 tooth in the T-45? Ford replaced my T-45 and I am not sure if they could have put a GT class trans in or if it would be the correct Cobra one. It does say Tremac on the side (98 production). If it has a 7 tooth than I suppose I could use a 21 tooth (From ford) for 3.73's?
 
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