The ultimate differential thread

Given recent revival of the E-Diff delete "debate" I figured it would be nice to have a single thread amalgamate all the information around not only E-Diffs but just differentials in general.

This is a bit of a spur of the moment thing so my first post is not going to be too in depth but I plan to add more and more info over time.

With this out of the way.

The F360 had a mechanical (clutch type) differential regardless of transmission choice and the F430 had an E-Diff again without regard to transmission choice.

The E Diff also uses clutch packs like a mechanical type LSD in order to bind the output shaft speeds to the differential housing speed, this is what creates a "limited slip" action.

The clutch packs in a differential operate in much the same way as the clutch in a manual transmission car in that the two or more plates, half connected to one side of the drive line, the other half to the other, meet together and through friction, torque/energy/movement is synced between the two parts.

The way the clutch packs in a differential operate differently than in a manual transmission is that in a transmission, without pressing on the clutch pedal in the cabin, the clutch mechanism is forced together by the pressure plate and this is the maximum pressure between the flywheel/clutch that there will EVER be. By pressing on the clutch pedal, you're disconnecting the engine from the transmission.

In the clutch type LSD, the clutch packs sit between the output shafts (towards the axles) and the housing (the driveshaft side). Normally there is SOME preload provided via a spring/washer but in the steady state, low torque/coast scenario the clutch pack sees the MINIMUM amount of lockup it will ever see. Only when there's a large torque through the drivetrain (you're either on the throttle or high rpm engine braking) will the clutch packs bind (depending on what ramp angles you have in your LSD, the 1 way, 1.5 way, 2 way etc.)

See @67bmer 's great post here https://www.ferrarichat.com/forum/posts/148046230/ (please DO check out his post, it's also got a bunch of the above info and LOADS of pictures which I haven't found anywhere else as it's a tear down of a 360 LSD)

The key takeaway here is in a differential, if the clutches "see" a lot of binding pressure (or more precisely, ANY friction between the output shafts and the differential housing), the differential "limits" slip between the two output shafts (i.e locking up). If there is NOT a lot of binding pressure, the differential acts as an open diff.

Now with all the technical bits about a regular ol clutch type LSD out of the way ... the F430 E-Diff

The E-diff is "kind of" like a mechanical clutch type LSD in that it has a pack of clutches. What's UNLIKE a traditional clutch type LSD is that the clutches do not engage via torque from the engine via a ramped/cammed carrier. Instead the clutches are actuated via hydraulic pressure driven by the F1 pump. Furthermore there's only one set of clutch packs which connects the left hand side driveshaft to the housing (there really isn't anything "wrong" with this design and it won't cause "more lock on one type of corner vs the other", just worth noting) as you can see in the parts diagram here

https://www.eurospares.co.uk/Ferrari/430/F430_Spider_(RHD)/PartDiagrams/0034/DIFFERENTIAL_AND_AXLE_SHAFT

also, because internal pictures/documentation on the E-diff in the F430 is SO hard to find , here's Matt Armstrong's video of his F430 rebuild, timestamped for convenience, there's about 2-3 minutes of differential coverage

While it wouldn't be impossible to design the internals that would still operate mechanically with ramps/cams exerting mechanical pressure onto the clutch pack in the e-diff, I find this extremely unlikely because the whole point of the E-diff was the thesis " a mechanical LSD allows for only one lockup profile which is not ideal for all situations, sometimes you want more lockup sometimes you want less, so a hydraulically actuated electronically controlled system allows for optimum lockup all of the time" (in theory) ... to have a "base lockup profile" that cannot be "turned down" works in the complete opposite direction from this design theory.

Now with that said, this is not to say the E-Diff is a gift from god brought to us from the heavens by Prometheus. Being an electronically controlled device, it's only as good as the software behind it no matter how good the design is theoretically in principle. Also, it was built by the italians, who historically don't make the best electronically controlled anything and reliability of their hardware (which doesn't involve burning petrol in cylinders) also leaves much to be desired.

Apparently many F430s are suffering from a combination of issues relating to the above and neglect, all of which result in the E-diff locking/binding up more than it should, for more of the time than it should. This leads to bad shifting (as it "consumes" more of the hydraulic pressure form the F1 pump, leaving less for the actual shifting mechanism), bad handling because you're effectively running an LSD that is constantly running on a very very high preload (or in the worst case, like driving around with a welded diff), etc. Allegedly even mundane things like using slightly different sized tires (well within the realm of normal deviation for any other car ~+/-2%) would throw the E-diff software into a hissy fit because it has very precise/narrow band of acceptable differences in front/rear rotation speeds.

This has lead to offerings in the market to disable the E-diff electronically (Scud Ing Swiss SEB ECU) or outright delete of the system in manual (or convesion) cars.

It's objectively true that if you're suffering from some or all of those negative issues then a delete or disabling of the e-diff WILL enhance your experience (unless the only thing you do is try to drift your 430 out of a cars & coffee meet). For most people, most of the time an Open diff is better than a welded diff.

Now with that said, it's very very very difficult argument to make that a disabled E-diff is better than a properly functioning E-diff. That is a stretch by any and all standards. Someone telling you this is for sure trying to sell you something, plain ignorant, or trying to mislead you for very very niche reasons (they're helping you with a manual conversion, but because preserving the E-diff requires some software changes which are hard/pricey and they don't want the additional cost/headache).

Someone telling you the E-diff deleted will still act like an LSD is at BEST being extremely misleading (technically even a bit of preload gives a bit of binding and thus can deliver differential torque .... but realistically an open diff has friction too and can probably deliver differential torque to the tune of 55/45% split) and at worst, they have absolutely no idea what they're talking about and you should run the otherway if they ever offer to work on your car.

Taking all of this into account, if I had a 430 and had a perfectly functioning E-diff ... would I disable/delete it ? No. Not unless I was doing a manual conversion and I was told (sincerely/genuinely) that there was no software solution to allow me to keep the E-diff functionality. If it's working, aint no way I'm voluntarily getting rid of it unless the only "solution" was extremely cost prohibitive. If it's not working well, chuck it. Mechanical LSDs aren't that expensive and even leaving it as open wouldn't really be something I would notice the downsides of unless I was regularly operating at traction limit and fractions of a second of being able to apply throttle matters.

 

All the challenge cars had a mechanical lsd fitted

Made by zf if I recall correctly

 

https://f430parts.com/products/221704-220949-lsd-differential-bevel-set-40-9-4-44-ferrari-f430

 

The E-Diff is the same on both manual and F1 cars.

1) What was OEM is not neccesarily good, you wouldn't run 90s tires on a 355 just because it was "OEM"
2) If the stock/OEM component is working, then sure, why get rid of it unless you had to
3) If and when the E-diff fails, it can fail in a way which makes shifting much worse on an F1 car. If it fails in the "locking up too much/too often" it will simply lead to bad handling regardless of what transmission you have. You can fix it and pay for all the F1 pump/hydraulics/etc. to be refreshed .... but the design is such that it's useful service life is not particularly long regardless of mileage, you see systems failing with or without miles on the car so it seems like after a certain amount of time, it just goes. Getting a mechanical LSD and ripping out the F1 could be financially more sensible than repair AND it will be more reliable going forward.
4) On a conversion, the software rewrites/flashes neccesary to keep the Ediff ARE tricky, everyone can make their own decision if it's worth it if they have a perfectly functioning E-diff, but if yours ISN'T running, it's not much of a decision

 

Not sure what you mean here.

As far as I know, converting from F1 to manual AND keeping the ediff would require both hardware (not particularly difficult, just blocking off the ports that went to the shifting mechanism) AND software changes and it's the software changes aren't straight forward, apparently there are many different versions and not all are compatible with whatever version ecu/tcu/etc.

If I'm mistaken, would appreciate if you can add some more in depth detail for the thread so everyone else can use it. I'm not a 430 owner but I kind of fell into this rabit hole after watching a recent conversion video on youtube.

 

Ah, ok so we're probably in the same camp then of "it can be done, but you need to know what you're doing"

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What about a challenge diff transplant?

 

I'll add more technical info into main post on this after but does anyone know if any ferrari has ever had a torsen/helical/gear type differential standard from factory?

The explanation for how these work is notoriously awful on the internet. If the word "worm wheel" or "worm gear" are ever mentioned you should dismiss everything before and after.

 

To be fair, open diff cars corner just fine... Just not on throttle =)

I'm not gonna lie, I'm guilty of driving a 500+hp super car like a grandma.

I live in Hong Kong and our roads are ****, tight and on the side of a mountain... I have no wish to be buried in my 458... and having crashed my MX5 (which has about 1/4 the power) into said mountain, I'd probably be entirely OK with having an open diff 430 manual spider.

With that said, I entirely understand that doing so would justifiably be seen as "cheaping out" in the same way that I viewed the lack of dealer service history on my 458 spider when I bought it as "cheaping out"... regardless of whether it was ultimately true or not. Your car will always be ranked against its contemporaries and there are a LOT of owners who meticulously go through their dealer for any and all things.

 

That's what started this whole thing

He is stating something incorrect confidently

 

Here's a forum (it's in German but the pictures are universal ) post with lots of info

https://www.carpassion.com/forum/thema/60887-funktion-einer-steuerbaren-differentialsperre/

It's abbundantly clear from the teardown on this forum that unlike a mechanical LSD there is no mechanism/device to exert mechanical clamping force on the clutch pack (it's ALL hydraulic). While there must be some preload in the system to achieve the correct backlash, this is going to be a negligible influence on lockup characteristics under load.

If you walk through the teardown of the E-diff from the pictures in the above post (i'm not sure what the policy on straight up steeling photos from other forums here in this situation) you'll see it's actually just simply an open-diff with a hydraulic clutch pack on one side. It's not particularly fancy.

Here's a stock image from ferrari showing the clutch pack

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Note there's only one set of clutch packs on the E-diff as opposed to a left side and right side set on every other mechanical LSD. Nothing inherently wrong with this design, the clutch pack when actuated will bind the left hand side axle to the housing, but by doing so it will also be implicitly binding the right hand side axle to the housing as well (remember that the average rotation rate of both axles must equal the rotation rate of the housing itself, so if you limit deviation on the left, you're also limiting deviation on the right).

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clutches are basically always a serviceable items