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Discussion Starter #1 (Edited)
Ever since GWR first posted about plopping an ND rear diff equipped with LSD (the only limited slip option available at the time) into their 124, I had my eye on doing something like this. Having an extra diff laying around for a more serious LSD like the Cusco or OS Giken, along with an OEM part through the remainder of warranty is a good idea, too. So I did some research, ran some numbers, looked up parts and pricing, and... someone was parting out a 124 Abarth! w00t! I said "shut up and take my money" with speed, and picked up a decent low mileage OEM LSD. Right in the middle of racing off-season, too, which means I actually had time to put it in!

Installation took the better part of a weekend, working on it on-and-off, taking notes, taking pictures, and getting my son (who was on spring break from his Precision Machining Technologies education) to help out. I think if I did it again, it would easily be under 6 hr., and with a lift, climate control, and beer (or root beer for my under-21 assistant) wench, perhaps down to 4.

Oh yea- as you're reading this, let me just say, if it looks too hard, it probably is. If something looks heavy enough to end you (like the rear subframe) assume it will if given the chance. And my ramblings below are in no way intended to replace a competent mechanic with proper tools and the Factory Service Manual. Consider these my observations, and take them with a grain of salt.

Okay, that said, this installation can be done without a lift, and with basic tools, ramps, jack stands, and an impact wrench (I have a cordless electric for zipping wheels on and off, and it worked great). You'll also need a torque wrench as things start coming back together, maybe new gasket washers for the diff plugs, and new snap rings for the half shafts. It's probably a good idea to replace the exhaust gaskets on each end of the mid-pipe too, but our own 124 has less than 10,000 miles on it, so I reused those.

So here's pretty much what I did...

First, back the car up onto a set of ramps.
Leave it in gear, but parking brake off (because you'll be removing them).
Chock the front wheels.
Disconnect the negative battery cable.


Put a pan under the rear diff.
Remove the fill plug from the diff, then the drain plug. 23mm and 24mm sockets. Allow the diff to drain.
Clean the magnetic drain plug. Replace plugs.
Drain and fill plugs = 35 ft/lb.
Fluid cap = 0.6 L (give or take - just 'till fluid spills from fill w/ diff level). When refilling, we used Mopar 75W85 Synthetic GL5 meant for rear diffs with LSD. If Ashland offered it in the US, I'd have used their 75W85 GL5, but you can't get it in the US.


Crack loose the lug nuts (80 ft/lb). Jack up the rear and support it with suitable stands just so the tires are off the ramps.
Remove the rear wheels.


Remove the rear ABS sensors (2 screws each) from the hub support and lay them back out of the way. (75 in/lb)


Remove the brake calipers and hang them out of the way.
Caliper bolts = 15-18 ft/lb


Remove the brake caliper brackets with pads.
Caliper Bracket bolts = 38 - 48 ft/lb


Remove brake discs.
There was a step in the FSM about removing the auto leveling sensors, however I have a Classica, which does not have the fancy headlamps.


Remove rear sway bar end links from the aft link (28 ft/lb), but leave on the bar. Remove the (4) nuts holding the sway bar on the chassis (14 ft/lb) and remove the bar, with end links, chassis brackets, and bushings.


Remove the left rear plastic aero panel (4) screws (80 in/lb).


Remove the right rear plastic aero panel (one clip and 3 screws - 80 in/lb)


Remove the left and right parking brake cable brackets from the subframe (20 ft/lb).


Using an impact gun, remove the hub nut from the half-shafts


Remove the (6) M12 bolts holding each hub to its links (50 - 60 ft/lb).


Remove the hub.
I've seen notes elsewhere about having to give the splines some love to break them from the hub (screw on a nut just about level with the end of the shaft, hit the end of the shaft with a copper hammer), but that wasn't necessary in our case. I'd suggest a tiny dab of anti-seize on the splines (NOT THE THREADS, which could adversely affect your torque readings) during re-assembly to make any future work easier.


Pop the half-shafts out of the diff. I used a pry bar, being careful not to slip and damage the boots. You have to break it past the snap ring, which requires some force. It's a good idea to replace the snap rings, in case they're distorted or otherwise damaged from removal.

Remove the Y-shaped and X-shaped undercarriage crossmembers that are under the trans and prop shaft.
Place a jack under the transmission to support it.
Stuff a rag between the bottom of the diff and the subframe to support it.


Remove SEVEN of 8 nuts holding the PPF (Power Plant Frame, the big aluminum thing that travels along the prop shaft). The one nut you're not going to remove is special, because the stud it's attached to is actually pressed into the PPF. That one is the lower driver side (left) one attaching to the diff. Loosen the nut and unscrew it just so it's flush with the top of the stud. Next, use a hex socket to unscrew that stud from the diff, and the PPF will be lowered as a result (and the diff should stay level because of the rag or rubber pad you've got supporting it). The important thing is to keep the two parallel so you don't damage the threaded hole in the diff as you remove the stud.


And out comes the PPF. Don't forget to put it back. It looks important. ;)

Next comes the exhaust mid-pipe. Unbolt it at both ends, and remove it. The muffler is far enough back to stay on, since the sway bar was removed.

Unbolt the propeller shaft from the rear diff., (4) nuts and bolts (40 ft/lb). Hang the rear of the propeller shaft out of the way (no need to remove it from the transmission)


Loosen all the nuts holding the subframe (aka crossmember) to the chassis but do not remove (they'll go back on to 85 ft/lb). Taking all the nuts down about 10mm (3/8") is useful, so you'll know when the jack is supporting it.


Support the subframe with a jack that can be lowered to near the ground. Have a helper balance the subframe while the nuts are removed. Continue supporting the subframe from tilting, and slowly lower the subframe to the ground. It's freaking heavy, so use caution, and don't remove nuts from underneath, only from beside.


Gently slide the subframe out from underneath the vehicle.


The rear diff is held on by four nuts atop a rear differential mount, which is attached with two screws to the subframe. Remove the mount, and the diff is free to be replaced. Check the torque on the studs atop the diff - they should be about 15 ft/lb. The nuts go on to 45 ft/lb. The mount to chassis screws should also be at 45 ft/lb.

Most of our new OEM Mopar parts come from AllMoparParts and the rear diff mount is from Deyeme Racing.

That about does it! Installation is pretty much the reverse.
The hub nut should be installed snug, then torqued to spec when you're able to prevent the hubs from rotating. The FSM states to get it to about 75 to seat it, then loosen 180 degrees, then take it to 175 - 202 ft-lb. The nut isn't castleated and there's no locking pin (kinda freaks me out) so I'd follow those instructions pretty religiously. Aside from that and the interesting way they press that one stud into the PPF, it's really just a whole lot of wrench-turning.

Hope this helps. Feel free to ask anything, and I'll do my best to answer.

I'm eager to see a OSG or Cusco LSD install into an ND / BA housing. i'm curious to know how technically involved it is, or if it's crack the egg, put in the new yolk, and button it back up. If it's that easy, everyone that wants a street-friendly Abarth LSD has some resale potential in their open-end diff.
 

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Discussion Starter #6 (Edited)
I have people.

Greg
Me, too. And my son really was helpful. He's not JUST a teenager. And I think it is good for those less equipped (people or tools) to know that it can be done shade-tree mechanic style. When I do instructional write-ups for parts we sell, I try to avoid special tools and lifts unless it can't be avoided. The good news is, you can "try this at home" so-to-speak, which means only spending $1500 on the LSD instead of $2k+ on the LSD plus the shop labor and supplies (I think it works out to a 4 hour job + they'd want to do an alignment, too).

It's been damp and cold so far with the LSD installed, so I think I can say pretty early that if we get stuck with a "wet" event (Solo2 race doesn't stop just because it's raining) the team and I will REALLY have an advantage.

EDITS:
I know I'm on the clock with fixing what's in that post before it's frozen in time, so if you see something stupid, feel free to point it out. A good example I noticed was "Hang the rear of the diff (oops, I meant propeller shaft ) out of the way"
 

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Discussion Starter #8 (Edited)
Any idea for a diff cooler?
I always get inspired while I'm wrenching on something. As I was removing the plastic shields in front of the diff, I noticed that one had a bit of a curve to it, where it seemed to be intended to direct some air up into the rear diff area. I'm wanting to do aero shields front to back like I made for my Dart (for the front only, so far).

It's polycarbonate, made to replace the flimsy polyethylene and fiber pieces, and light shines through it, so I put amber LED strips up under there.

Anyway, something like that. Multiple pieces, front to rear, smoothing the undercarriage as much as possible. But there are some places that need to be able to grab a little air, like for the rear diff. Not quite sure what I'd do there, but I do indeed plan to do something. First, I need to measure diff temps when the ambient temp is warmer, and I can get it out on a highway drive. I'll need some baseline numbers so I can see how much of a difference the stock pieces really make. That way, when I add more aero pieces, I can make sure I'm not screwing up rear brake thermal recovery or differential temperature. I have to say, from what I've taken apart so far on this car, it's very thoughtfully engineered.

Now, that said, I have my hands full already for this race season mod-wise, so I'm not sure how quickly I'm going to get back to laying under there scratching my chin over it, lol!
 

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I applaud your skill and the wonderful photos of the process. This was no small task given how our cars were designed. It looks like the differential was not intended for "casual" replacement.
In a former life I auto-crossed a Datsun 510 and needed a LSD to make it competitive. That job was much more simple since I was able to just disconnect the rotational bits and then drop the differential. I was alone when I did this, which was foolish, and thought I could just drop the differential on my chest and then work myself out from under the car. Not so. That standard small-case unit was a lot heavier than I expected and since the garage floor was painted and very smooth, I found myself without any traction! I was flat on my back, stuck between the jack stands and couldn't just chuck it off. Fortunately my neighbor was outside and I was able to call him over. After he was done laughing at me he grabbed my ankles and was able to pull me out from under the car, thanks to that slick floor.
I'm glad your install was less dramatic!
best regards
Pete
 

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Discussion Starter #10
@pikeman yea something like that was my nightmare, which is part of why I got my son to help. I knew I could "probably" get the subframe down on a jack by myself, but why risk it? It was easy for me to be the muscle and hold it in case it tried to tip, and my son to lower it down. Trying to reach beyond your center of gravity, work the jack, hold it steady... nope. Glad I didn't try to go it alone.

I still have the OE diff, and am interested in cracking this egg to see what's inside, but it's not like a diff I'm used to, being more like a tiny transmission or something rather than a big round housing with a "lid" bolted on the back. It's amazingly light weight, though, which is cool. Bet it would be lighter with some titanium fasteners ;) heehee

I'll probably pick up a LSD from Good-Win when it's time to get something more heavy duty to deal with the slicks I'll eventually have for racing, but I think the OS-Giken or Cusco options might be a little to "grabby" right now, especially with my wife still driving it on the street.
 

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I always get inspired while I'm wrenching on something. As I was removing the plastic shields in front of the diff, I noticed that one had a bit of a curve to it, where it seemed to be intended to direct some air up into the rear diff area. I'm wanting to do aero shields front to back like I made for my Dart (for the front only, so far).

It's polycarbonate, made to replace the flimsy polyethylene and fiber pieces, and light shines through it, so I put amber LED strips up under there.

Anyway, something like that. Multiple pieces, front to rear, smoothing the undercarriage as much as possible. But there are some places that need to be able to grab a little air, like for the rear diff. Not quite sure what I'd do there, but I do indeed plan to do something. First, I need to measure diff temps when the ambient temp is warmer, and I can get it out on a highway drive. I'll need some baseline numbers so I can see how much of a difference the stock pieces really make. That way, when I add more aero pieces, I can make sure I'm not screwing up rear brake thermal recovery or differential temperature. I have to say, from what I've taken apart so far on this car, it's very thoughtfully engineered.

Now, that said, I have my hands full already for this race season mod-wise, so I'm not sure how quickly I'm going to get back to laying under there scratching my chin over it, lol!

Fiat transmission is NC sourced as we know and we have run 300 hp through them for years without additional cooling....except when we did flat bottoms. Did two NC with flat bottoms....started with just NACA ducts blowing on trans and that proved not enough, I blew one to bits at Chuckwalla Raceway. Went to a scoop for trans and diff in the flat bottom and that worked. On the ND we don't plan to do full race at this time so we will not bother with flat bottom but we will do an air scoop on the diff in the Fiat because same diff in the ND got too hot in early testing and we now have air scoops on the Turbo ND's trans and diff. Will have those simple scoops in production soon, will try them both on the Fiat soon.
 

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Ever since GWR first posted about plopping an ND rear diff equipped with LSD (the only limited slip option available at the time) into their 124, I had my eye on doing something like this. Having an extra diff laying around for a more serious LSD like the Cusco or OS Giken, along with an OEM part through the remainder of warranty is a good idea, too. So I did some research, ran some numbers, looked up parts and pricing, and... someone was parting out a 124 Abarth! w00t! I said "shut up and take my money" with speed, and picked up a decent low mileage OEM LSD. Right in the middle of racing off-season, too, which means I actually had time to put it in!

Installation took the better part of a weekend, working on it on-and-off, taking notes, taking pictures, and getting my son (who was on spring break from his Precision Machining Technologies education) to help out. I think if I did it again, it would easily be under 6 hr., and with a lift, climate control, and beer (or root beer for my under-21 assistant) wench, perhaps down to 4.

Oh yea- as you're reading this, let me just say, if it looks too hard, it probably is. If something looks heavy enough to end you (like the rear subframe) assume it will if given the chance. And my ramblings below are in no way intended to replace a competent mechanic with proper tools and the Factory Service Manual. Consider these my observations, and take them with a grain of salt.

Okay, that said, this installation can be done without a lift, and with basic tools, ramps, jack stands, and an impact wrench (I have a cordless electric for zipping wheels on and off, and it worked great). You'll also need a torque wrench as things start coming back together, maybe new gasket washers for the diff plugs, and new snap rings for the half shafts. It's probably a good idea to replace the exhaust gaskets on each end of the mid-pipe too, but our own 124 has less than 10,000 miles on it, so I reused those.

So here's pretty much what I did...

First, back the car up onto a set of ramps.
Leave it in gear, but parking brake off (because you'll be removing them).
Chock the front wheels.
Disconnect the negative battery cable.


Put a pan under the rear diff.
Remove the fill plug from the diff, then the drain plug. 23mm and 24mm sockets. Allow the diff to drain.
Clean the magnetic drain plug. Replace plugs.
Drain and fill plugs = 35 ft/lb.
Fluid cap = 0.6 L (give or take - just 'till fluid spills from fill w/ diff level). When refilling, we used Mopar 75W85 Synthetic GL5 meant for rear diffs with LSD. If Ashland offered it in the US, I'd have used their 75W85 GL5, but you can't get it in the US.


Crack loose the lug nuts (80 ft/lb). Jack up the rear and support it with suitable stands just so the tires are off the ramps.
Remove the rear wheels.


Remove the rear ABS sensors (2 screws each) from the hub support and lay them back out of the way. (75 in/lb)


Remove the brake calipers and hang them out of the way.
Caliper bolts = 15-18 ft/lb


Remove the brake caliper brackets with pads.
Caliper Bracket bolts = 38 - 48 ft/lb


Remove brake discs.
There was a step in the FSM about removing the auto leveling sensors, however I have a Classica, which does not have the fancy headlamps.


Remove rear sway bar end links from the aft link (28 ft/lb), but leave on the bar. Remove the (4) nuts holding the sway bar on the chassis (14 ft/lb) and remove the bar, with end links, chassis brackets, and bushings.


Remove the left rear plastic aero panel (4) screws (80 in/lb).


Remove the right rear plastic aero panel (one clip and 3 screws - 80 in/lb)


Remove the left and right parking brake cable brackets from the subframe (20 ft/lb).


Using an impact gun, remove the hub nut from the half-shafts


Remove the (6) M12 bolts holding each hub to its links (50 - 60 ft/lb).


Remove the hub.
I've seen notes elsewhere about having to give the splines some love to break them from the hub (screw on a nut just about level with the end of the shaft, hit the end of the shaft with a copper hammer), but that wasn't necessary in our case. I'd suggest a tiny dab of anti-seize on the splines (NOT THE THREADS, which could adversely affect your torque readings) during re-assembly to make any future work easier.


Pop the half-shafts out of the diff. I used a pry bar, being careful not to slip and damage the boots. You have to break it past the snap ring, which requires some force. It's a good idea to replace the snap rings, in case they're distorted or otherwise damaged from removal.

Remove the Y-shaped and X-shaped undercarriage crossmembers that are under the trans and prop shaft.
Place a jack under the transmission to support it.
Stuff a rag between the bottom of the diff and the subframe to support it.


Remove SEVEN of 8 nuts holding the PPF (Power Plant Frame, the big aluminum thing that travels along the prop shaft). The one nut you're not going to remove is special, because the stud it's attached to is actually pressed into the PPF. That one is the lower driver side (left) one attaching to the diff. Loosen the nut and unscrew it just so it's flush with the top of the stud. Next, use a hex socket to unscrew that stud from the diff, and the PPF will be lowered as a result (and the diff should stay level because of the rag or rubber pad you've got supporting it). The important thing is to keep the two parallel so you don't damage the threaded hole in the diff as you remove the stud.


And out comes the PPF. Don't forget to put it back. It looks important. ;)

Next comes the exhaust mid-pipe. Unbolt it at both ends, and remove it. The muffler is far enough back to stay on, since the sway bar was removed.

Unbolt the propeller shaft from the rear diff., (4) nuts and bolts (40 ft/lb). Hang the rear of the propeller shaft out of the way (no need to remove it from the transmission)


Loosen all the nuts holding the subframe (aka crossmember) to the chassis but do not remove (they'll go back on to 85 ft/lb). Taking all the nuts down about 10mm (3/8") is useful, so you'll know when the jack is supporting it.


Support the subframe with a jack that can be lowered to near the ground. Have a helper balance the subframe while the nuts are removed. Continue supporting the subframe from tilting, and slowly lower the subframe to the ground. It's freaking heavy, so use caution, and don't remove nuts from underneath, only from beside.


Gently slide the subframe out from underneath the vehicle.


The rear diff is held on by four nuts atop a rear differential mount, which is attached with two screws to the subframe. Remove the mount, and the diff is free to be replaced. Check the torque on the studs atop the diff - they should be about 15 ft/lb. The nuts go on to 45 ft/lb. The mount to chassis screws should also be at 45 ft/lb.

Most of our new OEM Mopar parts come from AllMoparParts and the rear diff mount is from Deyeme Racing.

That about does it! Installation is pretty much the reverse.
The hub nut should be installed snug, then torqued to spec when you're able to prevent the hubs from rotating. The FSM states to get it to about 75 to seat it, then loosen 180 degrees, then take it to 175 - 202 ft-lb. The nut isn't castleated and there's no locking pin (kinda freaks me out) so I'd follow those instructions pretty religiously. Aside from that and the interesting way they press that one stud into the PPF, it's really just a whole lot of wrench-turning.

Hope this helps. Feel free to ask anything, and I'll do my best to answer.

I'm eager to see a OSG or Cusco LSD install into an ND / BA housing. i'm curious to know how technically involved it is, or if it's crack the egg, put in the new yolk, and button it back up. If it's that easy, everyone that wants a street-friendly Abarth LSD has some resale potential in their open-end diff.
Hi everyone,
I've done this job myself in the past few days, and I've found this thread extremely useful.
Only I few things I can recommend:

- Loosen the hub nut BEFORE removing rear callipers (see pic 1).
As a matter of fact I pulled the parking brake very hard while doing it and still the nut was extremely tight that I had to step on the long 1/2 inches wrench you see in the pic.
Without the aid of the parking brake I can't imagine how much UNDUE stress I would have gotten on the half shaft and the rest of the transmission (with the gear inserted as instructed)
As you can see I didn't even had to remove the spacers to fit the 32mm socket.

- For those who have self levelling headlights.
Make sure to disconnect the connector and the nut indicated in pic 2 (rear left wheel-well) otherwise you're going to strip it off while lowering the heavy crossmember..

- Last make sure you get yourself a powerflex (or similar) "rear diff mount insert" kit before doing this job so you'll save a lot of hassles when time comes (and it will sooner or later) to replace those OEM parts...

That's all I have
Thanks everyone

Patrick
 

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I'm actually planning to do this swap soon and your instructions are very helpful. I'm just wondering, where did you get your torque specs from? My service manual is missing a ton of torque specs as well as the entire rear subframe removal procedure. I wonder if it's because I have an older version of the manual.
 
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