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Fitting locking rear diff to non locking Sport SC

5K views 10 replies 3 participants last post by  mpetersen3 
#1 ·
I have an 07' RRS SC and need to replace both diffs after getting it stuck in a swamp for an hour (rear has a clanking sound and wheel judders when turning at high angles), front diff is leaking. My mechanics opinion is they both should be replaced with remanufactured originals. I would love to turn this lemon of a situation into lemonade. I've been considering getting an ARB locking diff for the front for a while anyhow... is it possible to fit a rear elocker diff (one of the ones that would've been an HD add on)? It seems like the major snafu might be not having the right wiring on my harness already. I've tried looking at the related threads here but didn't find anything specifically confirming or denying.
 
#2 ·
Also it seems like my options are dealer remanufactured for ($1400 front, $1600 rear non locking - they wouldn't quote me locking).
I'm also considering having mine rebuilt and having an ARB air locker added to one - $990 for locker - no word yet on cost. Is there a consensus on front vs rear in terms of best place to add an ARB? It seems like the rear should turn less in any given corner since it will track inward sooner.
 
#4 ·
I would be surprised if you developed diff issues sitting in swamp water for an hour or so - the diffs are sealed quite well and have extended breathers. What evidence (other than your mechanic's word) that the diffs are faulty. Was there water in the oil?

The symptoms you mentioned could be almost anything in the drive system, especially if the underneath has not been thoroughly cleaned to remove grit etc.

I would be getting a second opinion.

The OEM electronic rear diff has been retro fitted but is not a simple process.

Garry
 
#5 ·
The symptoms are thus, I can see the rear wheels individually judder / skip when reversing or going forward while turning at or close to full lock. My front diff has a leak. My local junkyard has used ones (non locking) for $500 each. Stealership remanufactured were ~$1300 and ~$2100 for front and rear (non locking) plus a substantial core charge (1-2k I think). I can get the rear locking assembly for around $300 on ebay and an aftermarket motor for ~$200. My current thinking is the following... buy a rear locking diff and motor and try to reverse engineer the signal and manually fit my own switch in the cab. I had a LR engineer unofficially tell me it is just a PWM signal to control lock, the motor or locking diff control module could be reverse engineered (I have a bachelors in EE - so competent enough to figure out and or build an imitator). I've found the module for $50.

It seems like I can use the GAP tool to enable the locking diff in my computer - whether the module can be wired into my loom is the question I think - I need to figure out if it runs on the can bus or has its own special wiring from the TR module. I'll call the GAP guys and see if they know.

I am weighing flushing the front and either sealing in place with RTV or finding a replacement gasket (can I replace the gasket without pulling the whole diff? I'm such a noob in some ways).
 
#6 ·
This is the most comprehensive info I've found on it.
https://expeditionportal.com/forum/...-manual-rear-locking-differential-lr4.168031/

It seems like the custom control PWM route would be the way to go if I was going https://discoweb.org/index.php?threads/lr3-rear-diff-rebuild.93253/

Rebuilding the front/rear seem like painful options

https://www.rangerovers.net/threads/leaking-front-differential.41778/ - this and the SSM mentioned therein suggests that the front seal can go bad due to a bad breather that causes pressure buildup. In my case the breather was probably submerged when I got stuck. I'm wondering if a breather upgrade, flush and RTV seal hacking might be enough for my front.

Right now my head is spinning with options - I'm leaning toward flush and seal the front (if RTV isn't a no-no) and buy a used rear and have someone do it - no locker.
 
#8 ·
Pirate and the portal forums may be OK but I dont know - do a search on either (not sure which one - probably the D3 one) https://www.rrsport.co.uk/forum/ or https://www.disco3.co.uk/forum/ as there is a full thread that covers everything required to retrofit the e-diff to the vehicle.

But then you can fit an ARB diff lock to both the front and rear of your vehicle.

As far as I am aware, the diffs have breather extensions as standard and these end up in the engine bay somewhere so unlikely a breather issue. However I am not so sure so you need to confirm elsewhere.

Garry
 
#9 ·
I finally found what I've been looking for http://www.disco3club.co.uk/gallery/albums/userpics/10170/E-diff Fitment.pdf

I haven't replaced the diffs yet but am getting close to doing the job. After watching a youtube diagnosis of a defender's diff issues I've realized that I can put the car up on stands, unhook the driveshaft sfrom the T-case and rotate the diffs manually to narrow down the source. I'm hoping to do that soon. My front diff leak seems quite apparent, the back diff fluid was milky (cloudy) brown when I drained it, which I believe is the result of taking on water no?

I'm also wondering if anyone knows how to inspect the CVs for any issue either after or before pulling them, I don't think they are binding since this clunking is occurring consistently on relatively flat surfaces and not at all when driving straight (regardless of surface). I know to check the shafts where they mate into the diffs but am unsure of how to validate that the ball bearings and internals are ok.

I'm probably leaning toward getting an ARB rear locker and swapping both diffs and all CVs, as a precautionary measure but just to be done with it, though I'm still considering the glory route of integrating the HD rear locker. The reason for its appeal is that from my understanding it is an electronic variable locker - so theoretically the performance should exceed that of the ARB air locker as it can function as a LSD. If anyone knows more or cares to speculate on this I would love to hear it.
 
#11 ·
I wanted to post an update, the dealer replaced my CV but the issue persisted. They recommended replacing the t case but quoted me $7k. Before heading to a junkyard to do a swap myself I stopped by a local mechanic. He said the t case should have codes so we checked and it did. A general t case issue code I don't recall. One of the possibilities for the code was the t case clutch was miscalibrated. We ran the calibration routine and my juddering issue disappeared entirely. I haven't tested the low range or locking yet, but the issue is completely gone in high range.
 
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