I've been able to link the thud on my vehicle to the rear e-diff locking when at stops, and unlocking as you drive away, as long as the center e-diff is locked also. The rear e-diff will usually unlock fairly quickly when driving away from a stop in a straight line. But when turning or stopped on an incline, the center will be locked and the thud definitely happens then every time.

The center and rear e-diffs lock and unlock a dozen or more times on a simple trip down the street, as I recorded in the attached video. I'm making a left turn from a stop into a gas station. The thud happened around 8 seconds, but it's not audible in the video, since these thuds are more of a feeling than a sound. Note the the front wheel turn to when the center e-diff locks/unlocks.

 

Why do they have to constantly lock and unlock when driving on dry pavement.

l thought the diff locks were only needed when traction is reduced or lost.

 

Hi Zac431 and other forum members. Reporting back on the thud, clunk, judder a the right rear of my new Defender.
I took my new 2020 Defender to the dealer and showed them the Land Rover Technical Service Bulletin that mrmihai
had posted earllier, here's the link to it,
https://landroverforums.com/forum/20...-sound-114622/
My dealer said that Bulletin is not in their system, however they were able to find one in their system that is updated and
deals with the issue I was experiencing. As mentioned previously, I was both hearing and feeling what could be called a
thud, clunk or judder intermittently at the right rear of my 2020 Defender. It was most noticeable when making a left turn which loaded up the right rear suspension.
Of course, when I took it to the dealer and took him for a drive I could not get it to make the noise, which was maddening.
I left it with them and told them to perform the rear diff double flush as noted in the Land Rover Tech Service Bulletin, even
if I had to pay for it. Thankfully they were able to take it on a drive themselves and did hear and feel the same thing I was.
They performed the work under warranty and it appears that has solved the issue for me, although I am keeping an ear out
in case it presents itself again. Knowing what I know now about the rear diff and potential wear of the clutch packs causing
oil contamination which is generating this issue, I would recommend doing a double flush of the rear diff fluids as called out
in the tech bulletin every 30,000 miles, especially if you are driving a little sporty. Mine had approximately 37,000 miles.
I appreciate my dealer covering this under warranty as the cost to have them perform this outside of warranty is very high.
I thought about also changing my transfer case and front diff fluids at the same time, outside of warranty, however have
decided after hearing the very high cost from my dealer, I will learn how to do this myself when ready.
Note: If you don't have a rear locking diff configuration on your new Defender, this service may not apply to you as the
rear diff may not have clutch packs in it ​​​​, (not exactly sure if this is the case or not).
I have posted my original post below and another post too for easy reference. Many thanks to Zac431 and the forum members helping out
to find the issue. I am disappointed it did not solve Zac431's similar issue. DaBull

My original post tread on this was Thud at right rear
I have a light thud, clunk and judder sounding noise vibration from the right rear. I can both hear the thud, clunk and judder and feel it too. I thought at first perhaps the wheel nuts had come loose and checked them and they were are tight. The thud clunk judder tends to happen when I make a left turn going slowly, which loads up the right right suspension. It also sometimes happens when I am just driving slowly in a straight line and lightly accelerate. The madding thing is that it does not happen all the time and I have not been able to reproduce it when I want too. It just happens on its own, although as mentioned above, most of the time it is when making a slow left turn. Of course, when I take it to the dealer I cannot get it to repeat. The dealer said they checked and tightened down the suspension components, however that did not help. My thoughts have gone from it maybe being an air suspension strut, shock, wheel bearing, rear differential. I am still under warranty and want to make sure it gets taken care of as it is happening more often as time goes on. Has anyone else experienced this or have some idea of what it might be. I am taking the car back to the dealer in 2 days and would like to give them some ideas to check out. Thanks, DaBull

Hi zac431 and other forum members responding to my post about the Thud at the right rear of my new Defender.
Thanks to your posts I did more searching and came across another thread that included a post from mrmihai that I have posted
the link to below.(Thank you mrmihai). He found and posted a Land Rover Service Bulletin regarding the rear diff,
(See link below to thread that also includes the service bulletin). Evidently, the rear differential 2 clutch packs become
contaminated with clutch debris from wear on the clutch packs and they are recommending flushing the rear diff twice
with new oil to remove the contaminated. One of the forum members in one of the threads I came across, also
said he also smelled burnt oil, and I have had the same smell, although not every time I hear the thud or judder in the rear.
When I do smell it, it is right after I hear the thud. I am taking my new 1st Edition 2020 Defender into the dealer tomorrow,
Wednesday 11/15/2023 and will be handing the dealer the service bulletin. I will report back my findings after
they perform this service and check everything else out. Going to have them flush and change the fluids in the center and front diffs too,
even if I have to pay for those two. My mileage is at 37,000. I love this forum! DaBull
To view the Lad Rover Service Bulletin, go to post 5 under the thread link below.
https://landroverforums.com/forum/20...-sound-114622/

 

Hi Zac431, Did you do a double flush as recommended or just a single flush of the rear diff fluid? See my post #13 below.
My double flushed worked. Many thanks for pointing me in the right direction of finding the issue. I am hopeful your
situation will resolve itself. If you are still under warranty, perhaps they will replace the rear diff. DaBull

 

I wonder about this also...

 

"l appreciate my dealer covering this under warranty as the cost to have them perform this outside of warranty is very high"


Why would it be so expensive to change the differential oil, surely 30 minutes work and the cost of the oil.
Remove drain plug, drain oil, replace drain plug, remove fill plug, fill with new oil, replace plug.

One hour if the tech is slow. Once in a ramp l could do this job on my old Defender in fifteen minutes

 

I have this exact issue - dealer took a look at it today and say the 'transfer case' needs an oil change and saying it must have been heavily used (13k mile car I bought in July), but the symptoms seem to match when the rear diff switches from lock to unlock at low speed turning - I told them when dropping it off. They can't change the fluid until Feb which is ridiculous and reading this I think it's the wrong diagnosis anyway. It was 2 months to look now 2 months to try to fix, it's eating into my warranty!

 

Sounds more like a rear diff clunk.

I changed my oil on the rear diff and transfer case recently. Rear diff is now a quieter. It is something I'll be doing every so often from now.

It's a very simple DIY on the rear diff. Don't even need to remove any under armor or use a lift. Just whack it up to max height on the rear and crack a door. less than an hour work. 20 mins if you're efficient. I am not.

Here is a how to. Dead simple