D4 Any Added Value of Rear Diff lock over TRS?

[David Hannett]

Hi All
I am having to replace my 6 mth old D4 due to it being a write off - (ingested water engine hydraulic lock) but thats another story ...
Question is should I go for the rear Diff lock option this time around? - Is there additional value in having the rear diff lock beyond what the standard TRS functionality provides to justify the added cost and wait time for delivery from the factory?
cheers

[Tote]

Depends on what you are doing....
I've got one on my D3 and I reckon its worth it for that last 5% of traction when you really need it. I've got a mate with a 100 series cruiser, dual diff locks and lifted 2" on 33"tyres and on the really tough stuff the Disco is it's equal despite the smaller tyres. My thoughts are that the diff lock contributes to this.
If you dont often need this sort of capability save yourself the wait and the $1000 and dont specify it. I think it would also make the vehicle a little easier to sell when you want to as well.

Regards,
Tote

[isuzurover]

IMHO - yes - if you will be taking it on the beach/mud/difficult terrain.

Have a read of the last 2 pages of the independant vs live axle suspension thread (if you can wade through the BS).

There are a couple of quotes from puma owners, and a vid of a RRS offroad. From the quotes and the vid you can see that the stop-start/not completely smooth action of the ETC/TRS causes you to lose some momentum, which can hamper your progress in some conditions offroad. The D4 system is likely better but it cannot be completely seamless otherwise they wouldn't have bothered with deeveloping the e-locker.

With a full locker this effect should not happen, unless both rear wheels have negligible traction and you are relying on the front.

[CSBrisie]

When I sold my D3, every second person (carsales.com.au) asked if it had the Rear E-diff...it didnt....I now own a D4 and ticked the $1050 option.

[WhiteD3]

I have a D4 on order with an e-diff. For $1000 it was an easy decision. I'm sure it'll add value to car when I sell it and will be handy in those very few instances where its needed.

[101RRS]

I saw a slighty used e-diff for sale on Ebay UK for $600 and was very tempted to buy it.

I know that they supposedly cannot be retrofitted but I cannot see why not - the wiring loom to hook it is up is most likely there and if the software is not already in the car, then the appropriate software update should fix that.

So for those in the know - why cannot the e-diff be retrofitted?

To the thread - if I was buying new I would spring for the diff.

Garry

[gghaggis]

I saw a slighty used e-diff for sale on Ebay UK for $600 and was very tempted to buy it.

I know that they supposedly cannot be retrofitted but I cannot see why not - the wiring loom to hook it is up is most likely there and if the software is not already in the car, then the appropriate software update should fix that.

So for those in the know - why cannot the e-diff be retrofitted?


Garry

"the appropriate software update" - there's several modules that would have to be re-flashed. Who's going to do that for you? Certainly not LRA. I doubt you could do it with a Faultmate - I recall a couple of guys in the UK trying to do this and they couldn't get the software, even though they had all the hardware to do a reflash. The wiring loom apparently had to be replaced, which meant stripping the upholstry and internal wiring down. They never reported that they got it going, so I assume it didn't work?

Cheers,

Gordon

[isuzurover]

"the appropriate software update" - there's several modules that would have to be re-flashed. Who's going to do that for you? Certainly not LRA. I doubt you could do it with a Faultmate - I recall a couple of guys in the UK trying to do this and they couldn't get the software, even though they had all the hardware to do a reflash. The wiring loom apparently had to be replaced, which meant stripping the upholstry and internal wiring down. They never reported that they got it going, so I assume it didn't work?

Cheers,

Gordon

Why can't you just fit the e-locker and install a switch to engage it manually???

IMHO that would be preferable, as you can decide when it is needed rather than the software.

With the e-locker engaged the rear TC will not activate, so I can't see any incompatability with any of the other systems if you have a manually activated locker.

[gghaggis]

The eLocker is not designed to be permanently locked, so I'm unsure of the implications to the diff itself or the axles. And of course, you wouldn't have the advantage of an infinitely variable lock, as per the OEM solution.

Cheers,

Gordon

[isuzurover]

The eLocker is not designed to be permanently locked, so I'm unsure of the implications to the diff itself or the axles. And of course, you wouldn't have the advantage of an infinitely variable lock, as per the OEM solution.

Cheers,

Gordon

So it doesn't lock solidly using a dog-tooth arrangement like other lockers?

Does it use friction plates like an LSD and just increase the pressure as needed?

It would probably be simple to pull it apart and check if it is up to the task of manual actuation.


EDIT:

Here is a pic:
http://www.cutawaycreations.com/IMAGES/car4/images/image1.jpg

The e-motor seems to end in a toothed gear which runs on the bronze coloured gear? Is that correct, or is it simply an in-out solenoid arrangement?

Ither way - looks like it would be simple to control it using an on-off switch or potentiometer type arrangement if you wanted variable control...


And here is the t-case/CDL - which appears to show an electric motor driving a worm gear which moves a selector fork
http://www.cutawaycreations.com/IMAGES/car2/images/image18.jpg

[gghaggis]

Ben - it's variable-pressure (via electronic control) - it never fully locks. I suppose you _could_ wire up a potentiometer + relay.

Garry - found the person who did a retrofit in the UK - turns out he _was_ finally successful and _did_ use a Faultmate!

If you go to:

Disco3Club The Discovery 3 and 4 Owners Club • View topic - Locking Diff retro-fit (http://www.disco3club.co.uk/phpbb/viewtopic.php?f=9&t=943&start=20)

you can download the PDF's explaining how he did it. Apparently cost him around 650 GBP.

Cheers,

Gordon

[101RRS]

Thanks Gordon - have booked marked it for reading in detail.

By the way anyone know the brand of diff in the D3??

Garry

[Graeme]

Ben - it's variable-pressure (via electronic control) - it never fully locks. I suppose you _could_ wire up a potentiometer + relay.
It uses a stepper motor to wind-in the pressure plate. I cannot see why it couldn't/wouldn't totally lock if the ecu thought the situation required it but setting-up software to emulate the ecu could take a lot of trial and error testing.

[isuzurover]

it never fully locks.

In that case I wonder why they didn't just fit an LSD. LSD+ETC is almost as good as a locker according to those who have compared the two in competition rock crawling.

[Redback]

Why hasn't anyone made a front or rear locker for that matter for the D3/4, is it because of how the drive system works??

OR

Is it because they think it won't be used in the tuff stuff like other 4WDs and why only a rear E locker from the factory:confused:

Baz.

[gghaggis]

In that case I wonder why they didn't just fit an LSD. LSD+ETC is almost as good as a locker according to those who have compared the two in competition rock crawling.

I guess to have it under control of the traction system, they wanted an electronic system. And according to LR, it locks to "99%", so more aggressive and much faster than an LSD.

Cheers,

Gordon

[Wilbur]

Why hasn't anyone made a front or rear locker for that matter for the D3/4, is it because of how the drive system works??

OR

Is it because they think it won't be used in the tuff stuff like other 4WDs and why only a rear E locker from the factory:confused:

Baz.

I think the ETC could get a bit of a headache if the diff was locked and it didn't know about it. The manufacturers of after-market diff locks probably wouldn't want to get involved in modifying the software.

[gghaggis]

Why hasn't anyone made a front or rear locker for that matter for the D3/4, is it because of how the drive system works??

OR

Is it because they think it won't be used in the tuff stuff like other 4WDs and why only a rear E locker from the factory:confused:

Baz.

Well, the factory already supplies an exceedingly good rear locker if required, so the aftermarket manufacturers would have a pretty small market - probably just not worth it.

And you don't need a front locker on a D3/D4 - they perform just fine with the ETC and Terrain response - in fact probably better.

Cheers,

Gordon

[Disco4SE]

I have a TR query.
Yesterday, I took my young bloke for some light off road stuff. I did a few culvert drains cross axled that had water in them and fairly slippery (Pirelli ATR tyres). Went extremely well.
I selected low range, S2, and raised the suspension. Went straight through without any slippage or noises from the transmission, wheels etc.
After doing this several times, I realized that I hadn't used the terrain response settings. I then selected Mud Ruts and went back through the same culverts. Every other setting was the same.
I then heard noises from the transmission, wheels etc.
I understand that it is the TR that creates 'the noises' , however the vehicle seemed to drive through the culverts perfectly without it selected :confused::confused::confused:
Cheers, Craig

[Disco4SE]

BTW : I forgot to add that I have the e-diff

[400HPONGAS]

The diffs are by STEYR same as the transfercase , my D3 S has the E-Diff , but being old school Id love some sort of indication of what it was upto !!
The e-diff has bigger CVs
https://www.aulro.com/afvb/images/imported/2011/02/1176.jpg
https://www.aulro.com/afvb/images/imported/2011/02/1177.jpg

[David Hannett]

Thanks every one for the helpful responses - appreciated

[rmp]

Terrain Response is always active whether a Special Mode has been selected or not. The extra noise once TR is selected would be Hill Descent Control which can be switched off with the yellow button.

Yes always buy the e-diff. It'll make the vehicle more attractive to offroaders who will always prefer, or sometimes mandate a vehicle with it.

The e-diff makes offroad life easier, esepically on hill climbs. Unfortunately, it cannot be manually locked for descents.

I reckon a front locker in the same way wouldn't go amiss.

[DiscoWeb]

I then selected Mud Ruts and went back through the same culverts. Every other setting was the same.
I then heard noises from the transmission, wheels etc.
I understand that it is the TR that creates 'the noises' , however the vehicle seemed to drive through the culverts perfectly without it selected :confused::confused::confused:
Cheers, Craig

Craig,

Perhaps the noises you heard were the ABS working in Hill Decent Control (HDC) mode which kicks in when in mud and ruts, even on small down hills, this could be the noise I can think of that would be "Activated" by using Mud & Ruts.

George

[Disco4SE]

Craig,

Perhaps the noises you heard were the ABS working in Hill Decent Control (HDC) mode which kicks in when in mud and ruts, even on small down hills, this could be the noise I can think of that would be "Activated" by using Mud & Ruts.

George
Yeah, could be right George, although there were other noises whilst cross axled that weren't without the Mud Ruts engaged?

Cheers, Craig