Rear differential clunk - how bad?

Hi, guys!

I have been having some clunking sounds in the drivetrain of my 2006 D90 and decided to fix it. I was really hoping it was not the rear diff and replaced the rear halfshafts, drive flanges and the prop shaft + the front halfshafts, cv joints, flanges (also the stub axles, bearings, brakes etc as we were at it).

I am sad to report that although now there is no more slack in the drivetrain and no jittering through the drive flanges etc, there is now a clear clunk as if two metal rods hit each other most of the times when I start moving from 0. I have also replaced the A-frame ball joint and that clunk is definitely in the rear axle.

From this I deduct that it is the rear diff that is worn.. but this sound makes me a little worried, may it mean that one of the teeth on the cogs is broken? Or how does the diff do that sound? It sounds like the splines are slipping at some point and hit the next cog..

I know it's silly to ask like that online, but does this make sense?

Sounds like the noise I had when my Disco 300Tdi broke two teeth off the diff crown wheel while we were in France! Drove it home and it ran OK, just clonked regularly which eventually began to get worse and became a regular, constant clonking and grinding sound, until I got it changed.

If it were me, I'd get a decent second hand diff ready to drop in, the job's easy if heavy. Then I'd take the broken diff out and check it is indeed broken at your leisure and maybe fix it or replace it with new.

Thank You, Paul! That was what I was thinking of as well. Glad You said that!!

Was the grinding from the broken off metal pieces in the diff casing?

Yeah, and 'cos I was towing a caravan for about 750 miles on motorways .. and not slowly!!

May I ask one more thing: that clunk comes around about the same time every time I start moving (lets say 1 second after depressing the clutch). Does it make sense? If one/more than one tooth on the crown wheel were broken, won't it clunk at different times until the broken tooth reaches the splines? I may be very wrong here

Easy answer, I don't know! It will be related to prop speed and road speed ... the crown wheel rotates same speed as the prop, but the half shafts rotate faster due to gearing.

Couple of questions ... Is your clunk only when setting off, is it every wheel revolution or related to road speed, or clonking sometimes when running, maybe over bumps or when turning?

I'm thinking trailing arm bushes at the axle, maybe Anti roll bar bushes, or even just suspension bushes if it's not related to road speed.

Thanks for thinking it through with me

The clunk is audible only when setting off, never while driving, never during upshifts or downshifts, turning or generally while already driving. Only when starting from standstill.

It could indeed be something in the bushes hmm..

Paul D said:

Easy answer, I don't know! It will be related to prop speed and road speed ... the crown wheel rotates same speed as the prop, but the half shafts rotate faster due to gearing.

Couple of questions ... Is your clunk only when setting off, is it every wheel revolution or related to road speed, or clonking sometimes when running, maybe over bumps or when turning?

I'm thinking trailing arm bushes at the axle, maybe Anti roll bar bushes, or even just suspension bushes if it's not related to road speed.

Click to expand...

to be exact, pinion travels at prop speed,crown wheel and half shafts 3.54 times slower

Thanks, James! Do You think this logic holds ground that if the clunk is audible only setting off, it is unlikely to be the diff?

Stock_90_TD5_SW said:

Thanks, James! Do You think this logic holds ground that if the clunk is audible only setting off, it is unlikely to be the diff?

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a clunk on take up could be diff cross shaft .slack in the cwp, worn center diff, worn bearings in intermediate gear and quite a few things more, id be carefully feeling the play in diff first bits cwp backlash then you can next feel play in diff itself

jamesmartin said:

to be exact, pinion travels at prop speed,crown wheel and half shafts 3.54 times slower

Click to expand...

Heh, absolutely right .. me's a dummy ..

I had a clunk when starting my newly rebuilt Defender. Really annoying after 3 years of weekends to have this happen !
Anyway, to save money i didn't replace drive flanges, drive shafts or diffs, thinking that I can 'easily' do this at a later date.
Everything, and i mean everything else is brand new or an upgraded part.

So, my assumption was the clunk was the flanges which i replaced.... clunking still !
So i replaced the rear diff with a new Ashcroft locking diff, new Halfshafts...... clunking still !!!! Wtf!!!!!!

SO i check, check and check all linkages by pushing and pulling everything. Nothing, all seems tight as should. Clunking still whilst driving over bumps.....

Anyway the moral of the story is that shaking things with your hand isn't enough force to reveal some clunking noises because what i did in the end was get my kind father to drive back and forth over the garage step to hear the noise better. Still not able to pinpoint it, however the noise was seemingly high up.

All it was in the end was lose bolts on the saddles that hold the 2 A-frame saddles the cross member. The holes are a little oval after 20+ years of use.

That's my boring story of the day, make of it what you want

PS. car drives like a magic carpet now. Yes !

Wow, windy81, thanks for this story! This part is really scary: "So i replaced the rear diff with a new Ashcroft locking diff, new Halfshafts...... clunking still !!!! Wtf!!!!!!" To put about 2k euros into it..

Could You guide me a little more into what those A frame saddles are? Something like this?

thats them

Stock_90_TD5_SW said:

Wow, windy81, thanks for this story! This part is really scary: "So i replaced the rear diff with a new Ashcroft locking diff, new Halfshafts...... clunking still !!!! Wtf!!!!!!" To put about 2k euros into it..

Could You guide me a little more into what those A frame saddles are? Something like this? View attachment 159988

Click to expand...

I intended to do this anyway, but it happened a lot sooner than i wanted! Skint yes but happy ! Winter is coming, kinda looking forward to it

Thanks a lot, windy81!!

I had a similar situation with the fuel pump. It was a burnt wire situation, but I replaced it. I think it's not a sunk cost, if You are planning to use the truck for some time still

Hope you get that clunking sorted

Sorry to bother with this again, but can anyone help me with the part number on this part?

The website I found yesterday says they are out of stock: https://yrmit.co.uk/product/hdg-frame-chassis-brackets-pair/

I don't seem to find it here either: http://new.lrcat.com/#!/1228/7683/10169/822 or here: https://www.landroverworkshop.com/diagrams/body-chassis/chassis/chassis-frame-assembly_52777

I would be very much obliged if someone could help me with the part number

Found them here a minute after posting this, sorry