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Discussion Starter #1
Alright so one piece driveshaft from the lincoln is on the way thanks to CDsDontBurn. Plan on trying to do the gear change at the same time just looking for some guidance on what all i need to attempt it myself. I know i need the 373s, the limited slip unit, speedo gear, also going to replace the cover(would the cover for the mustang that says ford performance across it from American muscle work for the bird?) What are some tried and true brands for these parts that dont break the bank?
 

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Not if it’s for a solid axle Mustang. The cover needs to be for an 99-04 IRS Cobra if it’s for one, it’s what the back of the differential mounts to cradle with.
 

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I believe you’ll need a purple speedo gear with 3.73’s. I wouldn’t recommend attempting a gear swap without guidance if you’ve never done one before.
 

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Discussion Starter #6
Might end up getting both those that you sent xr7, guess i just didn't see that cover yet thanks. Also not going to be by myself my grandfather who was a mechanic is gonna help me out
 

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You can only use one or the other, the brace is designed to fit the dimensions of the OEM cover, not the beefed up aftermarket covers. You won’t break the aftermarket cover.
 

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Also -- for your speedo gear, you'll need to take tire size into consideration to determine whether you need the 20 or 21 tooth. IME the 20 tooth is better with stock-sized tires; if your tires are a little smaller then the 21 tooth would be better.

Feel free to play around with my calculator to see the effects of tire size on best speedo gear: http://wannerweb.ddns.net/Public/TireCalc.htm
 

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Also -- for your speedo gear, you'll need to take tire size into consideration to determine whether you need the 20 or 21 tooth. IME the 20 tooth is better with stock-sized tires; if your tires are a little smaller then the 21 tooth would be better.

Feel free to play around with my calculator to see the effects of tire size on best speedo gear: http://wannerweb.ddns.net/Public/TireCalc.htm
So if you currently have stock tires and on 3.73 gears, but later get - say - 20in wheels, will that mean you'll have to pull the speedo out again in order to change the gear from a 21 tooth to a 20 tooth speedo gear?
 

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Depends on tire diameter. Most of the stock sized tires are about 26.5" in diameter. The formula for speedo gear teeth needed is wheel revolutions per mile x output shaft teeth x final drive gear ratio, divided by 1000.

E.g. a 225/60/16 tire with a diameter of 26.6" would have 757 rotations per mile: 757 * 7 * 3.73 / 1000 = 19.76 tooth speedo gear = 20 tooth.

Usually if the number is right in the middle, like my 255/50/17s (27" diameter, or 19.47 tooth) I round up the number rather than down, since as the tires wear, the speedo becomes more accurate. If I shave off 1/4" of tread from the diameter I would need a 19.6 tooth gear - so as you can see the 20 tooth is more accurate than a 19 tooth almost immediately, despite the math technically indicating a 19 tooth is better (by a small fraction) at full tread diameter. Remember, smaller tires mean more teeth on the speedo gear.

A 205/70/15 tire with a diameter of 26.3" is 767 revs/mile and almost a 20 tooth gear, exactly. So you'd need a pretty small tire to need a 21 tooth gear with 3.73s - 800 revs/mile or a diameter of only 25".

So as you can see, tire diameter matters when looking at speedo gears. At least, if you care about an accurate speedo. :)
 

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So as long as the next wheel / tire combination stays close to stock tire diameter size, it shouldn't matter, is what you're saying.

Sent from my Pixel 3 XL using Tapatalk
 

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Here's a calculator I've used forever:


There's even a listing with partnumbers for the gears at the bottom.

I think I have one of every color now, lol.

I have a pile of Green ones; those are popular in 2002 CV trannys.
 

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So dumb question here.

Is the speedo gear in the cluster, or is it somewhere else?

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It's in the tranny, attached to the Vss sender.
The sensor is held in with a 7/16" bolt, and held to the sender with a small clip.

All the english thread/size bolts are on the tranny, as far as I can tell. :)

You can pull it from underneath the car.

The gear rides on the matching gear that's on the tailshaft; Tranny's after 2003 don't necessarily have the teeth on the tailshaft, so they won't work without major rework.
Stock tailshaft gears are 7 tooth, 2002's are 8. (1998 and up, I think are 8)
 

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So a manual transmission won't need this gear at all, hence, the reason for a speedcal. Right?

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Discussion Starter #17
Good info that i will need haha, but the main thing was what are the better brands to use for gears and limited slip and also what else should i be replacing
 

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TracLok from Ford for the LSD; and FRPP (Ford Racing Performance Parts) for the gears.

Find a TL diff in the boneyard to rebuild, and rebuild the TL with the good parts (not sure if carbon fiber is worth the small upcharge or not; someone who does diffs for a living may be able to advise!) and with FRPP gears from almost any FRPP dealer (Jegs, Summit, Tasca, etc.)

RwP
 

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TracLok from Ford for the LSD; and FRPP (Ford Racing Performance Parts) for the gears.

Find a TL diff in the boneyard to rebuild, and rebuild the TL with the good parts (not sure if carbon fiber is worth the small upcharge or not; someone who does diffs for a living may be able to advise!) and with FRPP gears from almost any FRPP dealer (Jegs, Summit, Tasca, etc.)

RwP
So for the LSD / Trac-Lok, an FRPP is the first choice. Is that what you're saying? If one of those cannot be found, someone mentioned a Eaton Detroit Loker, 912A5621. Is that the one to get if an FRPP unit can't be had / found? What about an SCP unit? From the looks of it, it seems to be a Yukon unit. Do you (or anyone else) here know that answer?
 

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Well, the TrakLok may come from FRPP, but no; the GEARS from FRPP and I'd just dig for a Ford TrakLok for street usage.

I'm not fond of lockers on the street; diffs are there to let the two sides run at different rates around corners, and most lockers will chatter if there's enough torque going through the back on a corner. NOT a good deal in rain-slick streets or ice.

I can find TLs on Ebay and Amazon (!!!) easily enough new AND used.

Caveat: Needs to be one with the beveled spiders for a IRS; or the spiders need to have the bevels machined if not; or the cliprings removed from the half shafts; or you learn interesting unique ways to curse next time you have to pull the half-shafts.

RwP
 
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