How to change rear differential oil V6S - Non electronic LSD

G

GARETH

New member
My car is in its 6th year, but only covered 34k miles, plenty of them are short journeys, but also a few long distance Euro tours.

The rear diff has been thumping for quite a while now, so decided to change the oil.

First jack the car and support on axle stands. Access to the fill plug is tight. As you look from the rear of the car, it’s a small 5/16” hex drive plug, on the left side of the differential, towards the rear.

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Needless to say, before you drain anything from the diff, make sure you can undo this plug. You’d look pretty silly if you drained it then found you couldn’t remove the filler plug!

To access and remove the plug I used a 5/16 hex drive, on a 3/8 long extension and ratchet. If you feed the long extension along the rear of the drive shaft, you can get on the fill plug and undo it.

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Once it’s out, you can then use your 3/8 drive ratchet to undo the drain plug. It’s at the bottom of the diff.

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Obviously put your measured catch receptacle in place first and have a rag handy. Drain into the pot, I got about 700 ml of black, very black! oil out.

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Replace the drain plug and tighten to 25nm. That’s not very tight by the way, so I recommend using a torque wrench, and if you haven’t got one, don’t over-tighten it.

The oil I used was from Opie Oils, it’s the Motul gear 300 LS 75w-90 fully synthetic limited slip differential oil. It’s clear and green in colour!

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I used a Sealey hand pumped oil dispenser to fill the diff. Measure the correct quantity of oil into the pump (860ml) and simply put the pipe end into the fill port and pump all the oil in.

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Now refit the fill plug, it was a bit of a fiddle but once you get the thread started just use your hex socket via the driveshaft hole to tighten it to 25nm.

Clean up any spills, lower the car, job done, put the coffee on!
 
Erm not sure yet, not driven it. See other post about fill port. I might have to do it again with different oil, as I was lead to believe from my build spec that my car had a limited slip diff. According to pictures in other thread I might have an open diff!

No big deal, just will need to do it again with correct oil.
 
GARETH said:
Erm not sure yet, not driven it. See other post about fill port. I might have to do it again with different oil, as I was lead to believe from my build spec that my car had a limited slip diff. According to pictures in other thread I might have an open diff!

No big deal, just will need to do it again with correct oil.
Click to expand...

I thought yours was a 380? I recall your car being number 17798 (last part of VIN) in which case your build sheet says "REAR AXLE LIMITED SLIP DIFF". Again I thought all 380's came with limited slip diffs.

It might look different to the pictures because later models came with Torque Vector by Braking (seen as REAR AXLE LTD SLIP DIFF W/TVBB on TopiX).
Maybe.
 
Gareth, rest easy.

The V6 S of that vintage definitely had a mechanical LSD.

...the V8 S had the Electronic Active Differential from the start.
 
So has it cured the thump-thump in low speed corners? No not entirely. I’ve just been on a run, and it definitely is not as pronounced as it was, but it is still there.

Most likely to hear it as a low frequency rumble/thumping sound when turning sharply at parking speeds, especially when changing direction from a right to left turn (or vice versa)

Having read the technical description of the non electronic Limited Slip Diff, there is a lot going on in there, and a bit of mechanical harshness could be classed as normal. I’m not sure how many cars have the non electronic lsd? Perhaps explains the relatively low occurrence of this issue?

Anyway, I’ll carry on driving it and turn the radio up a bit! Shouldn’t be driving it slowly around car parks anyway!
 
Update. After a couple of days of use, I can say that this seems to have completely cured the low speed thumping from the rear.

Also seems to have restored the traction some what. It was very quick to spin a wheel from the line before, now it seems much more controlled. Perhaps the LSD was malfunctioning on the old oil?
 
Gareth,

As I understand it from my indie, the old oil remains in the clutch plates even when the diff is fully drained and new oil added. It takes a quite a few miles for the new oil to fully displace the residual old oil. Essentially, the "bass rumble" is the clutch plates slipping slightly due to the thickened, degraded oil affecting the friction. My issue improved as the diff warmed up thus reducing the viscosity of the oil.

I had the same effect, the "whomp" 85% sorted on swapping the oil, 100% gone and stayed gone after about 100 miles.

regards,

Rob
 
Yep that figures. Hopefully no lasting damage. It all sounds very similar to the torque converter judder issues that Discovery 3 owners experience. Lock up clutches skipping due to knackered oil. ZF recommend oil change on the 6 speed at about 70k, JLR say sealed for life!
 
Gareth.
I've just ordered some of the same oil you used from Opie oils with a view to changing my diff oil at 6 years and 28K miles showing, as a preventative measure not because of a problem.
Just wondered how yours is now you've used it more hopefully during the last few months since you changed it??
One thing that did puzzle me was you put in the stated capacity 860ml but only 700ml came out?? That's not caused any issues?? Leaks??
Thanks Stu.
 
No issues since, and it’s remained quiet with no leaks apparent. It’s due it’s 6 year service in a couple of months, I’ll be changing it again for what it costs. It will be interesting to see what condition the oil is in.
 
Gareth,
Thanks for replying so promptly, I'll crack on with mine once the oil and syringe to refill arrive then, let you know how i get on, be interesting to hear what your oil is like as you say when you drop it again.
Cheers Stu
 
When you drain your oil, drain it through a strainer to catch any bits. It will be interesting to see what you find. Old stocking would do.
 
Changed the oil today, as previously said, bit tricky especially with just Rear End on car ramps, only got 1/2” drive extension which is more cumbersome than 3/8” ( did try my 1/4 drive but the 8mm hex bit fell out and is lost in the crossmember/ bracing somewhere! 😞)
Oil was very black, but strained it through bit of old tights and pleased to find NO metallic particles at all👍🏻.
Refilled with exactly same amount as I drained out , bit of a faff as the Oil syringe I purchased wasn’t brilliant ( EBay £8) but managed it eventually.
Took it for spin and everything appears fine, tried slow speed full lock turns no noises
( weren’t any before either to my knowledge though)
Another bit of maintenance ticked off👍🏻
 
Thank you for the information on how too change the diff oil. I did this this afternoon and while I was there I freed up the exhaust valves.
Really good guide My 2015 v6s is on 22k miles, oil recovered from my diff was black, clean with no floater bits.
 
Did you use the original oil drain plug or replace it with a new one? If so do you have the Part Number?
Do either of the plugs - drain and refill - have compressible washers which need replacing/
 
No compression washers and no collar to compress a washer, so must be a taper thread. I did not replace either of the plugs, but did wrap some PTFE tape around the thread on each one, as there appeared to be some form of sealant on the plugs from the factory. I did torque up the sump plug as per the guidance on this thread. I will check the plug for any drips after a test run.
 
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