Rear e-diff retrofit to MY12 4.4 TDV8

The fault code P0900 that refers to open circuit on the brake clutch is also used for open circuit on the motor, discovered when my elder son rechecked the connectors in my fabricated section of loom and found that I had fitted the motor earth wire to an unused cavity, causing an open circuit for the motor. Correcting the motor wiring has overcome the reported clutch circuit fault and now both the motor and the brake clutch click momentarily each time the ignition is switched on or off, so more progress.

The only pre-fitting task left now is to have the module perform a self-check to calibrate. Clearing the module's faults after the motor wiring was fixed caused an unusual series of clicking noises from the diff compared with the short on/off clicking noises that now occur. It's plausible that the control unit may have done a calibration at this time but without any reference from other sources I cannot assume that the calibration has been done. The Faultmate Extreme doesn't currently support the self-check function even though some preliminary work has been done so I may have to piggy-back a subscription for my L322 onto an IID Tool.

Edit: As the e-diff has been successfully connected to the vehicle for a few ignition cycles and therefore no possibility of still being locked, the internal wiring will be finalised then reconnected to the e-diff to ensure pins have been transferred to the existing connector properly. The next step will be to swap diffs then swap the external harness but leave the fuse removed until calibration can be done as it will be safe to drive whilst waiting for a calibration.

Quote:

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Originally Posted by Graeme

The e-diff uses a motor that turns either direction...

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My earlier post on the e-diff's mechanical operation is incorrect and should be ignored.

A final out-of-vehicle test was to check that the diff showed locked in rock-crawl, which it did. Then after the pins were transferred from the temporary connector to the vehicle's connector the diff wouldn't show locked, presumably because the EPB had been disconnected to use the new external loom. The earlier test required the tail-gate locks to be closed before it would lock so no EPB is a plausible excuse. Next task is to re-paint the diff after cleaning-up the rust, corrosion and yellow paint that was applied to all bolts, nuts etc by the dismantlers.

RDCU connector housings (no contacts) can be bought from LR dealers or independent parts suppliers in the UK using the YPC numbers or from connector suppliers using the Tyco numbers. The connectors can be fitted with a secondary locking pin although LR don't always use them.

YPC114190 Tyco 1-967623-1 lock pin 967633-1 Purple 15-pin
YPC114170 Tyco 1-967621-1 lock pin 967631-1 Yellow 9-pin
YPC800350 Tyco 1355204-1 lock pin 967634-1 Black 17/18-pin (locator at pin 15)

As LR spare parts the yellow housing costs 10 GBP and the other 2 less than 3 GBP each. The yellow housing incl lock pin from Element14 was $1.26. Postage was the biggest cost.

I bought 30 965999-2 (30A, highest rating) contacts from Element14, Farnell UK's Australian operation for $7.15. 19 are required and I wanted more than 1 spare, not that there was a minimum or multiple order quantity. I found the contacts impossible to remove, not having the $45+frt special tool. I soldered the wires to the contacts as crimping would have required the very expensive special tool and multiple contact sizes for the mix of wire sizes.

The RDCU must be for the correct canbus version. Mine happens to be from a D4, only known by the markings applied by the dismantlers.

Its just as well it's you doing this Graeme. Anyone else would have enormous trouble and I bet it's absorbing a lot of your time. Do I detect another kit for retrofitting ED's coming out of this work? It would probably make a lot of people happy!!


I hope the RDCU is not as sensitive to the Can Bus version as the EPB is. An EPB from a later model car wouldn't work on my D4 because the Can Bus has been changed from my early 2010 model D4. We had to get the correct one for the VIN to get it to work.

I commend you on all the hard work. If it was me I think I would have just developed a standalone aftermarket controller...

The control unit part number is the same for D4s at least to MY12, MY10+ L320 and MY10-12 L322 and they all run the same s/w version. I consider that the system is working, just that the diff hasn't been fitted and calibrated yet. The diff showed as being locked when rock-crawl was selected so the control module was happy that it was communicating correctly with the diff electrics as required. Moving between neutral and drive caused clicking noises from the diff so with no faults now being recorded, I consider that all is well.

The canbus tappings can be anywhere on the HS canbus but IMO best that it be on the rear section as per the original wiring. The park brake canbus wires are conveniently in the same connector that the RDCU uses to communicate with the diff.

Buying new connector housings and new terminals is very inexpensive. A well-known wreckers wanted $175 for a used set with 150mm of wire from a wreck, justifying their asking price on their lack of availability and the cost of a crimping tool.

Being able to purchase the L322 harness that connects the EPB and the e-diff to the main chassis harness makes for a neat installation under the vehicle. However the complete harness could easily be fabricated providing the e-diff is purchased with both electrical connectors fitted - mine only had the main connector so the oil temperature sensor connector would have to be sourced.

I consider the retrofit is a straight-forward task and would be happy to provide insight gained to others.

Great job! I admire your ingenuity.

When I was shopping for a used D4 I would have opened up my search knowing that this could be possible down the track. Great work.

An expensive retrofit compared with the original extra cost if buying new and perhaps no extra cost if buying s/h especially if the seller isn't aware that an e-diff is fitted.