Speedo Gear part #

[pantera77]

So as I get ready to swap my K-code in, I forgot I need a new speedo gear. I know I need the white, 8 tooth drive gear with the 23 teeth. Does anyone know the part number?

[1987cp]

P72Ford may have a spare, or ask Lincolnmania. I had thought you had to go aftermarket for the 23 tooth gear (black?) ....

If there is an OE gear available, your cheapest source is probably your local Ford dealer.

[pantera77]

P72Ford may have a spare, or ask Lincolnmania. I had thought you had to go aftermarket for the 23 tooth gear (black?) ....

If there is an OE gear available, your cheapest source is probably your local Ford dealer.

Because I have a 90+ AOD I thought I needed the white 23 tooth. I'm planning on ordering one from the ford dealer, but I can't seem to find the part number.

[1987cp]

Your dealer can't provide the part number?

[88grandmarq]

23T gear is not a stock Ford gear, so I doubt any of the dummies at the dealer parts counter will be able to help you.
btw... you need the black 23T gear.
white (short snout) is for manual trans cars, black (long snout) is for auto transmission cars.

http://www.mustangsunlimited.com/SubCat.asp?CatKey=74-01&SubCategory=Speedometer+Components&SubSubCategory=Speedo+Gears&category=Drivetrain&KeyWords=LMF201

[pantera77]

23T gear is not a stock Ford gear, so I doubt any of the dummies at the dealer parts counter will be able to help you.
btw... you need the black 23T gear.
white (short snout) is for manual trans cars, black (long snout) is for auto transmission cars.

http://www.mustangsunlimited.com/Sub...eyWords=LMF201

Ok, so it's the black one I need then? I thought the black one was for the older AOD's that used the 7 spline one, and the white one was for the newer 8 spline ones like mine.

http://www.mustangsunlimited.com/itemdy01.asp?T1=DFM17271J+01&Category=Drivetrain&subCategory=Speedometer+Components&CatKey=74-01

That one is for a 7 spline AOD so I don't thin kit will work, or am I lost?

[1987cp]

Which generation of AOD you have changes only the number of teeth on your driven gear you need to work correctly with a given tire and gear combo. I got to take this into account when acquiring a 21 tooth gear to use with a C4 in a 3.08 geared car (it'd had an 18 or 19 tooth originally with its AOD). So far as I know, all C4 and AOD speedo gears interchange - the only caveat is to avoid gears designed for a manual tranmisssion, because they won't work.

[88grandmarq]

LONG snout driven gears are automatic transmissions, SHORT snout driven gears are for manual transmissions. there is no differenence otherwise.

Not sure how you calculated which gear you need, but you should be using this formula;

drive gear teeth x axle ratio x tire rev. per mile / 1000

Assuming you are running a stock tire size (215/70/15) it would look like this;

8 x 3.55 x 751 / 1000 = 21.32

in this instance you would need a 21T purple gear.

this is a good site to figure out what the tire revolutions per mile are;

http://www.miata.net/garage/tirecalc.html

[pantera77]

LONG snout driven gears are automatic transmissions, SHORT snout driven gears are for manual transmissions. there is no differenence otherwise.

Not sure how you calculated which gear you need, but you should be using this formula;

drive gear teeth x axle ratio x tire rev. per mile / 1000

Assuming you are running a stock tire size (215/70/15) it would look like this;

8 x 3.55 x 751 / 1000 = 21.32

in this instance you would need a 21T purple gear.

this is a good site to figure out what the tire revolutions per mile are;

http://www.miata.net/garage/tirecalc.html

Somewhere down the line I read a bad article I guess. Thanks for clearing it up. I guess It's good that I asked first then. I'll order one of those purple 21 tooth's right away.

[hav24wheel]

So, if I'm reading this right, I would need a 20T gear when I swap from my 3.08s to 3.73s?

[1987cp]

Possibly yes, possibly no. As another check, ask yourself what gear you have now, and whether it's reading accurately (I've managed to check mine against those police radar speed signs as well as newer unmodified vehicles). Not all speedos are reading correctly to start; one car I bought had a 16 tooth speedo gear and was reading about 5-7mph high at highway speeds. After popping in a 18 tooth gear, it was spot on. Incidentally, that 18 tooth gear came out of another car with the same tranny and rearend but 1" taller tires, that turned out to prefer a 16 tooth for some mysterious reason.

Anyway, assuming your speedo is currently reading accurately, look at what speedo gear gives the same ratio in teeth as your change in rear gear (i.e. a 21% increase in tooth number for your 3.08 to 3.73 swap). Ideally, you'll come up with the same tooth number by both methods.

[P72Ford]

I have that black 23T, which I bought at Mustangs Unlimited (think it was $20). I never installed it... shit I don't even know where I put it. All I know is, Scott put the purple gear in mine, and it reads too fast. But apparently the purple gear is correct for the older cars.

[88grandmarq]

So, if I'm reading this right, I would need a 20T gear when I swap from my 3.08s to 3.73s?

assuming you have a 7T drive gear and rear tire size is what is posted in your signature... you need a 19.79 tooth driven gear, 20T should work fine.

[1987cp]

Is there a 20 tooth gear?

[hav24wheel]

Yes there is a 20T gear. Its orange if I remember right.

And yes the info in my sig. Is right. I do think it is a 7T drive gear.