Rear Diff Repair/Replacement Options

[Ralph1Malph]

Hi All,
I/We have a longish road trip throughout Western QLD planned for August, so I'm trying to get the old girl in fighting shape.
She has a whiney rear diff with more than an annoying amount of lash that I'd like to address before setting out.
I'm assuming that my options are replace new, or replace 2nd hand. If the gears are worn, which I suspect, is rebuild or exchange an option or cost effective?
Has anyone done one recently and if so, willing to share indicative costs, trials, tribulations?

Cheers
Ralph

[Eric SDV6SE]

Haven’t had the pleasure, but a quick check on Rimmers shows a rear diff new is around 1600 bucks for OEM. If holding onto it for a bit longer, seems cheap insurance. I’m sure a tow from outback Qld back home would be more expensive.

diy fitting should be pretty straight forward.

[PerthDisco]

You can buy a diff rebuild bearing kit cheaply from AF and DIY it. 90% common it’s one cooked output bearing so you can swap over without getting into complex lash setups on the input side for which there is no LR specs on how to setup.

You can replace the input seal by carefully marking the lock bolt location and restoring to that exact position but try / hope to avoid any work on the input side.

[Eric SDV6SE]

You can buy a diff rebuild bearing kit cheaply from AF and DIY it. 90% common it’s one cooked output bearing so you can swap over without getting into complex lash setups on the input side for which there is no LR specs on how to setup.

You can replace the input seal by carefully marking the lock bolt location and restoring to that exact position but try / hope to avoid any work on the input side.

That makes a lot of sense, was not aware of the rebuild kits, good to know.

[PerthDisco]

That makes a lot of sense, was not aware of the rebuild kits, good to know.

Transfer Case also. It’s just a bag of bearings and a chain that are the main fail points.

Let us know how you go as this will be a common theme from now on with ageing D3s.

For some reason any rebuild info on diffs is unobtainium from LR so clever people have matched all the bearings into a kit.

Outback Disco had a crack at fully rebuilding his but probably could have just done the output side to fix the rumble.

LR3 / DISCOVERY 3 FRONT DIFF REBUILD - YouTube (https://youtu.be/L8iYJppRfwo)

[Arch]

Transfer Case also. It’s just a bag of bearings and a chain that are the main fail points.

Let us know how you go as this will be a common theme from now on with ageing D3s.

For some reason any rebuild info on diffs is unobtainium from LR so clever people have matched all the bearings into a kit.

Outback Disco had a crack at fully rebuilding his but probably could have just done the output side to fix the rumble.

LR3 / DISCOVERY 3 FRONT DIFF REBUILD - YouTube (https://youtu.be/L8iYJppRfwo)

His pinion bearings were totally shot as well. Any good diff builder would be able to rebuild one of those for you. While the specs aren't available, the principles remain the same...it just might not be cheap.

[Ralph1Malph]

Hi Again,
So to ease my confusion, as there are lots of videos and tutorials on D3 front diffs, but much less so for rear diffs, are they interchangeable?

I understand they will have the same rotational characteristics to keep all four feet turning the same, but are they the same beast ie, interchangeable?

My guess is no, based on how they are mounted and the fact they take different oils.

Cheers
Ralph

[Arch]

Front and rear diffs are different. There is a good rebuild description over on discoweb

[PerthDisco]

Front and rear diffs are different. There is a good rebuild description over on discoweb

Different configurations and look but exactly the same principle of one input and two outputs.

[PerthDisco]

In terms of a noticeable lash or clunk feeling emerging at 257k kms when changing down to lower gears at slower speeds have others also noticed this?

What are the normal culprits I should check and is it just a process of doing an inspection on the hoist looking for slop in driveline?

Gearbox is serviced and original so not to discount some harshness in the change that didn’t really change much after the last full service and change of the internal rubber mechatronic collars. Makes me think is elsewhere in driveline.

How do you determine if the output drive to TC spline is the culprit?

[DieselLSE]

How do you determine if the output drive to TC spline is the culprit?
By eliminating the easier to diagnose causes. A hoist would be handy, but not essential. Raise the car to off-road height, put axles stands or similar under the jacking points just in case. Leave the handbrake off and switch off the engine. The car will pop the gearbox into Park, but that's OK for this exercise. Crawl under the car and look for movement in the front and rear prop shafts. Both rotational and lateral. As the axles are prevented from movement by the wheels being in contact with the ground, and the gearbox is locked in Park, any felt clunking (and you will feel, see and hear it) will most likely be from prop shaft CV joints, splines or rear centre bearing or a combination of the lot. You might also pick up any diff slackness, too, but if you suspect that then I'd suggest getting an Indy to look at it. Unless you're feeling up to it, then you could jack up one rear wheel and see how that feels, then do the same at the front. That will also give you clues as to the state of the transfer case, but this is now getting a bit hard to explain.
Your prop shafts are probably due for replacement anyway, so I'd start there. Then adjust up the diffs if necessary. If all this fails, then start looking for more exotic causes.

[Ralph1Malph]

Hello,
Something I should have asked earlier is whether D3 and D4 and equiv RR are the same standard rear diff?
If they are, it just makes searches and kits and replacements easier to source.

Cheers
Ralph

[loanrangie]

Hello,
Something I should have asked earlier is whether D3 and D4 and equiv RR are the same standard rear diff?
If they are, it just makes searches and kits and replacements easier to source.

Cheers
Ralph

Different engines have different ratios so like for like should be ok.

[Ralph1Malph]

Different engines have different ratios so like for like should be ok.

Righto!
Prob should have realised that as well!

My thinking is, as my trojan has 320k on the clock, I'm considering a lower km swap as an option, hence the question.

Even tho a rebuild/exchange might only be 2-3k, I'm wondering if a the rest of the car will last that long and therefore little return on investment.

So, as I've a TDV6, I should look for a TDV6 or SDV6 diff. Makes sense.

Cheers
Ralph

[Eric SDV6SE]

Different engines have different like for like should be ok.

Hmmm, I'd be checking the transmissions and transfer cases used as this determines the final drive ratios to the differential.

6 or 8 speed boxes would make the biggest difference. Benefit is they're all ZF so the mounts and output shaft splines should be like for like.

[101RRS]

Ralph - if you google Land Rover Discovery Diff ratios AULRO you will find lots on this including the various diff ratios.

[loanrangie]

Hmmm, I'd be checking the transmissions and transfer cases used as this determines the final drive ratios to the differential.

6 or 8 speed boxes would make the biggest difference. Benefit is they're all ZF so the mounts and output shaft splines should be like for like.

diff ratios not trans.

[Arch]

Hello,
Something I should have asked earlier is whether D3 and D4 and equiv RR are the same standard rear diff?
If they are, it just makes searches and kits and replacements easier to source.

Cheers
Ralph

The D3 diff is different to the D4/RSS diff. While they are different, they are interchangeable. When looking for a rear lockers for my RRS I found that ARB made one for the D3 but not the D4. The D3 however bolted straight in to the RRS.