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I am interested in doing this for my Lusso.
 

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I remember at one point, I think on the Miata.net board, that someone did do a swap for LSD. I remember them saying that there are special tools needed to work in the diff and so it would be better unless you have really good experience to just swap out a complete diff, which is not an easy thing to do. I think maybe Goodwin racing might be able to shed some light on this?
 

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I'd be looking to a shop to do the install, possibly even Goodwin, I'd just have to drive the car down there.
 

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Discussion Starter #8
So I did some digging and I think I found the right MOPAR part. Here is the official MOPAR parts website: https://mopar.chromedata.com/NextGen/C1111#/landingPage

Use a VIN to pull up the car-- i grabbed a random Abarth VIN from Autotrader. For convenience, here's the one I used: JC1NFAEK4H0116928

Next, change the dropdown menu on the left from "parts" to "accessories".

Looks like the Abarth differential (68329082AA ?) costs approx. $750. Is that all that is required for the conversion? Am I looking at this right? Would love to get your thoughts on this.
 

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So I did some digging and I think I found the right MOPAR part. Here is the official MOPAR parts website: https://mopar.chromedata.com/NextGen/C1111#/landingPage

Use a VIN to pull up the car-- i grabbed a random Abarth VIN from Autotrader. For convenience, here's the one I used: JC1NFAEK4H0116928

Next, change the dropdown menu on the left from "parts" to "accessories".

Looks like the Abarth differential (68329082AA ?) costs approx. $750. Is that all that is required for the conversion? Am I looking at this right? Would love to get your thoughts on this.
The website would not accept the VIN you posted when just visited.
It's probably the GKN LSD found in the MX-5; and it's quite likely some shims will be needed to bring the ring and pinion gears back into proper mesh.
 

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The website would not accept the VIN you posted when just visited.
It's probably the GKN LSD found in the MX-5; and it's quite likely some shims will be needed to bring the ring and pinion gears back into proper mesh.
The link and Vin combo worked for me. Perhaps you forgot to select Fiat first.
 

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So I did some digging and I think I found the right MOPAR part. Here is the official MOPAR parts website: https://mopar.chromedata.com/NextGen/C1111#/landingPage

Use a VIN to pull up the car-- i grabbed a random Abarth VIN from Autotrader. For convenience, here's the one I used: JC1NFAEK4H0116928

Next, change the dropdown menu on the left from "parts" to "accessories".

Looks like the Abarth differential (68329082AA ?) costs approx. $750. Is that all that is required for the conversion? Am I looking at this right? Would love to get your thoughts on this.
I was able to pull up that car, but was unable to find a differential, or major parts for an LSD for $750. They list parts for over $2000 that aren't even LSDs. The part number you have is for a half shaft.
 

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The website would not accept the VIN you posted when just visited.
It's probably the GKN LSD found in the MX-5; and it's quite likely some shims will be needed to bring the ring and pinion gears back into proper mesh.
Big difference in final drive ratio between the ND MX5 and the 124.
 

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Big difference in final drive ratio between the ND MX5 and the 124.
The differential doesn't factor into the final drive ratio. Unless you are mistakenly referring to the final drive assembly as the differential.
Furthermore, a final drive assembly will cost much, much more than $750. The MX-5 final drive w/LSD is around $2000.
 

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Link from sleepy is correct, pretty much EVERYTHING we have done to our Fiat 124 is in our home forum build thread...CLICK HERE.

Page FOUR of that thread has our install of limited slip into our Classica.

We used the Miata rear housing with stock Miata limited slip because it was the only way at the time to get limited slip in the Fiat and lack of limited slip was holding back performance at Autocross events.

Yes, that meant the much taller Miata 2.9 FDR. Now our Fiat does about 67mph in 2nd gear, top gear and 2500 rpms is 75mph (gas mileage on long freeway drives is improved).

Our rear housing went to our friends at OS GIKEN for development of limited slip that fits the Fiat stock housing and FDR, hope to have those by Spring.

In the meantime, with big help from that Miata 2.9 rear with limited slip our Fiat took it's first Top Time of Day at BMW CLUB autocross in December. It beat every BMW, Porsche, Corvette, Miata, etc.

In addition to limited slip, that result took some other supporting bits including our light brake caliper conversions, light battery, and particularly these essentials:

RoadsterSport Suspension Package
Our Sway Bars
17x9 6UL wheels
Complete RoadsterSport Exhaust System (2.5 inch Crosspipe, 2.5 inch Midpipe, Quad Outlet Muffler Delete).

 

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I'd expect that the 2.9:1 rear end would work nicely, especially on a tuned car that has the torque to pull it at highway speeds without issue.

Once thing I liked about the S2000 (AP1) was that top of 2nd was around 104-106 km/h if you pushed it deep into the rev limiter. Rarely ever needed to shift to third in parking lot autocross events. Friends in early Miatas ended up shifting much more.

Runways was a different matter entirely. :)
 

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Has anyone (Good-Win?) investigated using an NC Miata LSD since it appears the ND differential isn't a go?
NC rear is unrelated, no plug and play.

Complete ND housing with limited slip can be used as we noted above but indeed ND limited slip internals need too much shim to fit the 3.4 FDR in the Fiat rear housing because they are made for the 2.9 in the Miata.. But in the coming months we expect both our OsGIKEN solution and Cusco for the Fiat housing with 3.4.
 
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