Thread: Rear e-diff retrofit to MY12 4.4 TDV8

All connectors and contacts are now on hand. Can-bus wires are nearby for the EPB module. Ideally the ignition feed would be picked-up from the original wire that supplies all transmission modules but will use the nearby EPB ignition feed.

It's time to mount the control module so that wiring can commence.

The control module has a home - nothing moved and using an existing bolt hole.

RDCU location.jpg


The control unit wiring harness is finished except for cutting the main power wire to length then fitting a 9.5mm female spade terminal to fit to the empty cavity in the connector in the rear fuse panel. A temporary EPB/FFH/e-diff connector is fitted to allow testing with the new external harness prior to fitting the diff itself. After testing, the pins will be transferred to the existing connector's vacant cavities and the new external EPB/FFH/e-diff harness will replace the current EPB/FFH harness. The free can-bus and IGN feed wires need to be attached to existing wires in the same connector.

RDCU harness.jpg

The diff was test connected to the vehicle today - in a wheel barrow behind the vehicle. A permanent clutch fault exists even though the clutch can be operated directly and there is 12V at the clutch pins in the diff connector. The fault may be due to the module and diff being from different vehicles and not yet calibrated so will get that done before looking further.

I minor hiccup was due to having fitted the canbus pins in the reverse order due to misreading the circuit diagram and ignoring the crossed lines close to the module. I now suspect the reason the transfer case control module is a canbus gateway is to keep the engine, brakes, gearbox and transfer case operating if a fault develops in the HS canbus further back in the vehicle, as the crossed wires shut down all the modules on the rear side of the TCCM.

Originally Posted by Graeme

The diff was test connected to the vehicle today - in a wheel barrow behind the vehicle. A permanent clutch fault exists even though the clutch can be operated directly and there is 12V at the clutch pins in the diff connector. The fault may be due to the module and diff being from different vehicles and not yet calibrated so will get that done before looking further.

I minor hiccup was due to having fitted the canbus pins in the reverse order due to misreading the circuit diagram and ignoring the crossed lines close to the module. I now suspect the reason the transfer case control module is a canbus gateway is to keep the engine, brakes, gearbox and transfer case operating if a fault develops in the HS canbus further back in the vehicle, as the crossed wires shut down all the modules on the rear side of the TCCM.

You can switch the diff lock on and off without the computer you say??

Originally Posted by chaybra

You can switch the diff lock on and off without the computer you say??

I am pretty sure I know what you are thinking, but the LR E-Diff is a progressively locking clutch system (whereas the Harrop e-diff is an electromagnetic locking centre) that the RDCU "learns" the open and closed limits required. If you didn't have those limits, you could run the risk of not having the diff fully open for normal driving

Originally Posted by Grentarc

I am pretty sure I know what you are thinking, but the LR E-Diff is a progressively locking clutch system (whereas the Harrop e-diff is an electromagnetic locking centre) that the RDCU "learns" the open and closed limits required. If you didn't have those limits, you could run the risk of not having the diff fully open for normal driving

What type of signal controls the locker? Is it a single feed to a spring returned clutch? or a full stepper motor?

Either way, a simple arduino board could control to either full lock or full disengage?

The e-diff uses a motor that turns either direction, a clutch that I suspect holds the motor or the mechanism to prevent turning and limit sensors. I expect that a simple control module could be programmed to operate the motor to the fully unlocked or fully locked position by honouring the limit sensors.

Obviously an e-diff would have to be the same ratio as the front diff.

My vehicle now reports/displays that it is fitted with an e-diff even though only the control unit is installed. No warning messages are displayed in rock crawl or when booting it in mud n ruts although the instrument cluster now shows the rear diff symbol but always unlocked whereas the centre diff shows locked.

I could have done with the e-diff again earlier today when progress at off-road height + Llams high was temporarily halted whilst crossed-up in deep, gravely bog-holes in the road, left after another 4wd was extricated on the w/e. Some back and forth shuffling then significant right boot, TC and lots of scraping noises saw the vehicle moving again.

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