Alright. Here's the final verdict. GET A SPEEDCAL! Make sure your gear is the stock one. That is all. I said this in the first reply. This is the best way for you.
Don't take this the wrong way because I cant believe this is still being talked about and so much wrong info is being posted here is horrible. I am apologizing in advance
there are 2 ways to adjust your speedo/OD with a pre 99 car either calebrate the puter when you tune it, or go to ford and buy a tranny sensor gear (like 8-10 bucks) prolly a 25 or 27tooth and i think its the red gear you'll need, i have a 23tooth red gear for my 3.73's and its spot on. if its post 99 the only way is a tune
Again to clarify the wrong posts like the one above.
YOU CAN NOT CALIBRATE THE SPEEDOMETER ON ANY 94-98 5 SPEED BY USING A TUNE. THE SPEEDOMETER IS NOT ELECTRONIC LIKE THE 99+
You want the cheapest easiest route. Stop listening to people who recommend plastic tranny gears for 4.30's that wear out overtime and arent accurate. 4.10's is the steepest gear a plastic tranny6 gear is accurate for.
youwin said:
i own a pair of 98's a V6 and a GT both had 3.73's put in
the v6 had a stock rearend gear of 2.73 and its tranny gear was a 17 tooth
the GT had a stock rearend gear of 3.08 and its tranny gear was a 19 tooth
EDIT: if your car has the 3.27 rear gear option then the tranny gear will prolly be different
More reasoning not to go off of that guy and get a tranny gear. He is basing the reasoning off a GT with a 3.08 gear, which had to be a 5.0 with a T-5 and not a Modular 4V with a T-45, being they did away with the 3.08 gear and went to the option 3.27 in 96 for the GT.
The 96-01 Cobras came with a 3.27 gear standard! That is the starting gear, not a 2.73 or a 3.08.
Just get a Speedcal like the rest of the world, minimize confusion from posts that show nothing but confusion because those posting in it don't have a clue either.
BTW, they dont make a 275/45ZR 17 tire and just assuming the difference in tire/rim size will fix it is also ridiculous.
I am starting to doubt some of the advice on the site.
Tom, blackfang is correct, the Speedcal is the way to go.
If you kept your tire selection and speedo gear the same, and went from a 4.10 to a 4.30 gear, you would adjust the dip switches to - 1000011001. That is the binary conversion for going from a 4.10 to 4.30.
Meaning when you pull off the cover, the 1st, 7th, 8th, and 10th dip switches should be placed in the up position. There is also an "ON" marked for the "1" or up position.
CASE CLOSED! Thanks for all the input, I mean we all make mistakes in trying to help others, the reason I kept asking questions was because I was getting CONFLICTING advice.
I agree it would appear the Speedcal is the easiest way to go. Thanks to all that attempted to solve my problem - I will go ahead and order one!
I have a 97 Cobra, The speedo was right when I got it (Oct 06) with 4:10 gears, I had it put back to near stock (3:31 Gears), I made the assumption that the driven speedo gear had been changed from the stock 19 tooth to a 23 tooth, but I was wrong (still the 19 tooth). The speedometer is slow by 25%. Any thoughts on how this was calibrated?(how I get it back?) It doesn't appear to have anything aftermarket hooked up. I lifted out the shift bezel, nothing unusual down there.