At 70mph my Sport has developed a sound that can conceivably be described as a Diff noise ....... the sound is constant and non grinding, more of a whirr??

If you ease off the throttle lightly the sound goes away upon reapplying the throttle the sound comes back? If you accelerate say to 80mph the exact same symptoms are there?

Below this speed the sound is not detectable.

This is a Sport running on 22" Overfinch wheels and tyres, not sure if this is a red herring or not?

 Mike

Mine does that too.

Interesting we have same model and year. What's the mileage on yours? Mine is only 35k. Does it sound as if it is coming from the rear diff? There is a ZF troubleshooting guide see here: http://www.disco3.co.uk/gallery/albums/use...0guide.pdf
which mentions on third from last page that these symptoms can be caused by an engine misfire fixable by updating the engine software.

It is easy and cheap to drain and refill the diff oil and the colour of the old oil gives you a good idea of the diff's condition. If it is is black that's bad news. Mine was OK. Front diff was FUBAR'd so has been replaced.

Not sure if I am imagining it but the symptoms on mine seem to have reduced considerably when I recently cleaned the MAP sensor and put some injector cleaner in the fuel tank (Millers diesel power ecomax). It is now quite bearable and really not a problem. Haven't tried the engine software update yet but it is on the list. Interested to know how you get on so keep this thread updated. 2008 MY Java Black TDV8 HSE

Cheers for the reply.

My mileage is 65K.

I will get the diff oils done for sure but this morning coming into work it really got to me. By going on and off the throttle all my passengers could hear it?? I don't have any faults indicated on the computer??

Will let you know more as I try to get it diagnosed. Mike

Hi chaps, realise this is an old thread but I have exactly the same noise, did you manage to resolve it?? Does the misfire in the document bring up a fault code, I have seen a significant drop in economy lately so could all be connected. Also at motorway speed with the cruise control on I get a gear change down when I hit a hill - most hills not just significant ones! Is that unusual or could be symptomatic of a misfire at speed??

Cheers

Alex TDV8 Java Black, Overfinch 22s

Alex,
We never heard back from Bullet11300 so don't know if he solved the problem.

In my case the problem still exists although it is only slight and even seems to come and go. The vibration is most noticeable at about 70 mph and manifest when accelerating. On lift off it is definitely less noticeable.

I have another issue which is that every now and again at about 70 mph the torque converter disengages and then re-engages again for no apparent reason (confirmed reading live values with a IID Tool).

So far I've tried gearbox flush, injector cleaner, gearbox adaptations reset, engine and gearbox software update, check of every electrical connection I can get to and even a new torque converter. There are no engine fault codes.

I don't know if the two issues are related or not.

The next thing I'm going to try is having the gearbox mechatronic tested and fitting a valve block repair kit as I suspect one of the valves is faulty. There are two specialists near me who can do this.

Your observation about the changing down on hills in cruise control mode may just be normal behaviour - re this quote from the workshop manual:

"Cruise Mode
When speed control is activated, the TCM receives a cruise active message on the CAN bus. The TCM activates a speed control map which prevents locking and unlocking of the torque converter clutch and minimises up and down shifts."

Your recent reduction of mpg could be just the cold weather putting greater demands on the engine power to drive all the extra lighting and heating and the FBH using more fuel. This has been discussed before.

Other suspects for causing the slight vibration are front or rear propshaft bearings and the differentials.

Hope this helps. Sorry it's a bit long-winded. 2008 MY Java Black TDV8 HSE

Hi Paddi

Thanks for the reply, really helpful. That line about the cruise is interesting, says to prevent locking and unlocking but that is exactly what mine seems to be doing. Same hill using foot throttle at same speed and there is no gear change.

Might start with a diff oil change, do you know if that is straight forward?? Can't see any how to info on the site. Just been reading about changing the front diff breather valve so will get that done too.

You are right on the ambient conditions affecting the fuel economy, even down to sensitivity to rain. Same drive in dry and wet at same speeds drop from 24.5 to 23.5mpg yesterday. kept all the sundries the same - lights on etc and external temperature was within 1 degree. Guess that is combination of drag on the tyres (brand new with loads of tread) and damp air. The same drive in summer has given me 30.4 and 27.4 in moderate traffic. (sad how i remember all this!!)

Cheers

AC TDV8 Java Black, Overfinch 22s

Alex,
No problem this is when the forum can be so useful to share thoughts on problems. The cruise map presumably locks the torque converter clutch as an economy strategy to maximise efficiency it also minimises downshifts but that doesn't mean it won't downshift at all if you go up a hill for example it should downshift but less readily than when not in cruise.

If your Sport is unlocking the TC without downshifting then that sounds the similar to mine and it MAY be a fault in the valve block. Alternatively it may be the TC slipping but in my case I've kind of eliminated that by renewing the TC. But before taking that drastic step you'd be well advised to just change the gearbox fluid and pan filter which is best left to a specialist. This often cures slipping TCs.

If the vibration is a fault with the diff then changing the oil is unlikely to fix the problem but draining the oil can be diagnostic as if the oil is black and there are lots of metal particles you know there is a problem (it may also smell 'burnt').

There is more than one 'how to' for diff oils on the Disco3 site; here is one:

http://www.disco3.co.uk/forum/topic54815.html

It is very easy to change the rear diff oil and a little more difficult to change the front diff oil as access is a little more fiddly but perfectly doable if you can handle a spanner and use a bit of ingenuity to refill it (I used a plastic tube with a small funnel).

Good luck - report back how it goes.  2008 MY Java Black TDV8 HSE