Discovery 3 e-diff

Diff behaviour hasn't changed this morning so the temperature sensor wiring problem must have been coincedental.
Looks like I have a failed actuator or a failing diff.........

Regards,
Ian

Changed the diff oil today and the diff was binding as it was backed off the hoist. A lap around the carpark with the new oil and it has been behaving itself. No actuator faults or error messages present since I did the rewiring so I think that that may have been unrelated. My strategy is going to be to change the oil again in a couple of thousand KM and see what happens.

Regards,
Tote

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Originally Posted by unseenone

As a non technical response, having seeing the inside of one of these diffs, I do not think that is entirely accurate. I believe that when the diff "locks" is is a locked differential. The "e-" in the diff is a clutch assembly, that spins a flywheel, which then engages with with teeth, that lock it. So, I think it is technically a locking diff when it is engaged, however, the computers tell it when to engage. I could certainly be wrong.

Pictured is some of the inner components, to include the actuator (e-) as well as the clutch plates, and a few other bits and pieces. A few more images are available, that would not attach for some reason.

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Thanks - great pics. However do you have pictures of the inside of the half of the diff hemisphere with the engagement wheel? I assume there is some sorrt of cam which increases the force as the wheel is rotated by the stepper motor? Ideally also measurements of the change in cam height through the full travel of the wheel?

The e-diff looks like it would suffer the same clutch plate wear issues as an LSD, and eventually become less effective or totally ineffective (as happens with most LSDs). It doesn't look like it would be hard to convert to a proper locker (with either electric or pneumatic operation) though...

If someone wants to lend me an e-diff - even a broken one, I can get some final year mech eng students to do it as a project.

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Originally Posted by isuzurover

If someone wants to lend me an e-diff - even a broken one, I can get some final year mech eng students to do it as a project.

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I don't think it would be hard to come up with a circuit that would lock up the diff completely, but then again a) it's not necessary, as the diff works brilliantly as it is and b) the components would probably have to be strengthened to cope with long-term 100% lock-up. One of the greatest advantages of this type of locker is the durability of the standard components in the rear drive-train when compared to the normal wear/breakage levels that many pure lockers either suffer or are a causal agent to.

What _would_ be incredibly useful, would be to override the centre eDiff controller, such that in emergency situations where one has broken a CV joint or halfshaft, it can be locked and the car is more easily drivable. I asked LR UK about this, but their comment was that it's not possible. I'm sure that statement could be proved wrong :twisted:

Cheers,

Gordon

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Originally Posted by gghaggis

I don't think it would be hard to come up with a circuit that would lock up the diff completely, but then again a) it's not necessary, as the diff works brilliantly as it is and b) the components would probably have to be strengthened to cope with long-term 100% lock-up. One of the greatest advantages of this type of locker is the durability of the standard components in the rear drive-train when compared to the normal wear/breakage levels that many pure lockers either suffer or are a causal agent to.

What _would_ be incredibly useful, would be to override the centre eDiff controller, such that in emergency situations where one has broken a CV joint or halfshaft, it can be locked and the car is more easily drivable. I asked LR UK about this, but their comment was that it's not possible. I'm sure that statement could be proved wrong :twisted:

Cheers,

Gordon

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I'm sure I could get a mechatronic student to do the latter as a project.

However I disagree with some of the first part of your post. While I am sure the e-diff works brilliantly now, for those who wish to keep their D3/4/RRS long term, the clutch packs will need to be replaced or reshimmed on a regular basis as they are a moving/wearing part - or the whole diff replaced at $3000(?) a pop.

MDE/ARB/Ashcroft etc lockers also have internals that are no stronger than LR HD diffs. The last generation MD locker used off the shelf LR side and spider gears, and the MD salisbury locker simply has splines added to the side of the hemisphere - no upgrading is needed. I believe ARB and ashcroft spider and non-locking-side side gears are the same as OEM too.

The e-diff already has upgraded axles, and is clearly a fairly sizeable 4-pin diff. I doubt conversion to a "proper" locker would increase the failure rate.

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Originally Posted by isuzurover

I'm sure I could get a mechatronic student to do the latter as a project.

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Good idea! (edited to add: it must be possible, because I recall the LR cutaway project in 2005 demonstrating an eDiff on a bench, with a 3-position switch to control it)

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Originally Posted by isuzurover

However I disagree with some of the first part of your post. While I am sure the e-diff works brilliantly now, for those who wish to keep their D3/4/RRS long term, the clutch packs will need to be replaced or reshimmed on a regular basis as they are a moving/wearing part - or the whole diff replaced at $3000(?) a pop.

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But the wear rate in terms of km's driven is probably only a fraction of that in the LSD or auto-locker setups, as it is only invoked rarely, and for very short periods of time. I've not heard of anyone needing to overhaul a D3 diff due to normal wear and tear. So contrary to your implication ("the clutch packs will need to be replaced or reshimmed on a regular basis") I don't believe there would be much call for such a service.

Quote:

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Originally Posted by isuzurover

MDE/ARB/Ashcroft etc lockers also have internals that are no stronger than LR HD diffs. The last generation MD locker used off the shelf LR side and spider gears, and the MD salisbury locker simply has splines added to the side of the hemisphere - no upgrading is needed. I believe ARB and ashcroft spider and non-locking-side side gears are the same as OEM too.

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Don't think that's true in the case of the Discos - my series 1 had different gears.

Cheers,

Gordon

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Originally Posted by isuzurover

the clutch packs will need to be replaced or reshimmed on a regular basis as they are a moving/wearing part - or the whole diff replaced at $3000(?) a pop.

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I suspect that several recalibrations could be needed over the life of the clutch pack as the ecu doesn't auto-adjust, but that's just a simple diagnostic function.

Is there a diagnostic function (T4, Faultmate etc) to lock the centre diff? I'll have a look at options with Faultmate next time.

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Originally Posted by Tote

Changed the diff oil today and the diff was binding as it was backed off the hoist. A lap around the carpark with the new oil and it has been behaving itself. No actuator faults or error messages present since I did the rewiring so I think that that may have been unrelated. My strategy is going to be to change the oil again in a couple of thousand KM and see what happens.

Regards,
Tote

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Sounds hopeful. How many kms since the oil was changed?

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Originally Posted by gghaggis

Good idea! (edited to add: it must be possible, because I recall the LR cutaway project in 2005 demonstrating an eDiff on a bench, with a 3-position switch to control it)

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Its only a 12V stepper motor so just needs the ability to cut power when there's excessive current draw to prevent the motor from burning out.

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Originally Posted by Graeme

Its only a 12V stepper motor so just needs the ability to cut power when there's excessive current draw to prevent the motor from burning out.

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That's the only real complication I could come up with, so this could be a plan. Simple switch on the transmission tunnel that activates and controls the stepper motor to lock the central diff. That way the car is drivable in cases of driveline failure. I suppose it could be fitted to the rear as well, but not sure of the advantages of that.

The only question would be what the rest of the systems would do - the feedback circuit is a little complex ...........

Cheers,

Gordon (more wine required)