Rear diff noise

[Rocket3]

I Need a bit of advice guys! The rear axle (diff.) was always a Little audible around 70mph, since i aquired the car (1998 XK8 120,00 miles) 4 years ago. It's getting steadily louder and present at anything over 40mph now. I will be looking out to Change this in the future but just how deadly is this noise?; a cog-like grumble, no clonks or Rattles. The noise does seem to calm down on really Long motorway trips though. Can I carry on for a while or is immenent death approaching? I drive the car only about 2000mls a year, but regularly 100 - 130mph (German Autobahn!) Is this just an annoying trait on elderly XK8's or am I playing with fire!?
Thanks for your comments.

[oldtimer]

Is there any oil in it ?

[J44EAG]

When was the last differential oil service carried out? Is there any other reference on the car documentation file to suggest the car has ever had a diff oil change?

Here is what I had taken out of my X350R at eighty thousand miles. Watery, broken down gravy. Useless for anything! Lubrication properties...zero!!

Mike K

[oldtimer]

Mike,
Are diffs another one of these sealed for life things ? The sad thing is that if it making a lot of noise the damage is probably done.

[Rocket3]

The oil Level has been checked and is Ok. There are no leaks, but no record of a diff oil Change. I will get this done if adviseable.

[J44EAG]

I recall seeing that diff oil change intervals are at 90k. Seeing the oil quality of the stuff taken from my diff at 80K, I personally think 60k diff oil changes would better meet the requirement.

Diffs are not sealed but there may be no fitted drain plug. In that case, the oil would have to be vacuum extracted as indeed was my own job.

It is also worth noting that gearbox oil change intervals are now set at 60k by ZF. Exceed at your peril....that is my own personal best advice.

For those with supercharged models, the Eaton service interval is also set at 60k miles. My own supercharger oil was changed late in life at 80k. The oil was vacuum extracted and found to be black. It was also outrageously smelly. It stank like rotten vegetation fermented in a human liquid product. Not nice at all and definitely in need of replacement.

We have high performance cars that need regular maintenance. Sadly many vehicles don`t receive it. Always check paperwork for documentary evidence that other oils besides that of the engine, have received the right maintenance. Just because a car has shiny paint, doesn`t mean to say it has ever had anything other than the odd stamped and irregularly applied basic or less, maintenance. Running a car into the ground without lubrication changes is not a wise idea.

Mike K

[Rocket3]

Thanks Mike, I will definately Change the diff oil now , but I suspect the damage has been done, which is annoying because all other Major servicework has been carried out inkl. fresh gearbox oil, complete cam chain assy, cooling / Waterpump new etc. Again, will a noisy diff hold out?

[J44EAG]

It might...but then again, it might not! This sort of thing never improves with use!!

Try Eurojag, Auto Reserve or ebay for a good second hand unit. You might be lucky and pick a good one up for a few hundred quid.

Mike K

[BrizzleJag]

Quaife offer a replacement/upgrade available on ebay; http://www.ebay.co.uk/itm/Quaife-Jaguar ... SwZQRYgiNe
DCR recon unit but almost the same price as a new Quaife unit; http://www.xk8-parts.com/2015/11/jaguar ... -assembly/
Used one on ebay; http://www.ebay.co.uk/itm/DIFFERENTIAL- ... SwOtBXTcMR
If you plan to keep the car long-term then it's probaby worth buying the Quaife unit.

[J44EAG]

Tom Lenthall supplies and builds Quafe units from his facility in Finchampstead.

You need to be well equipped and knowledgable to undertake either an OE rebuild or fitting of a Quafe. Don`t under estimate the work needed to drop out and refit a diff. They are mighty heavy and use of a ramp makes the work a whole lot easier.

Mike K

[Rocket3]

Thanks for info's. I won't be Tackling this Job myself. Luckily we have an excellent Jaguar specialist locally!

[mike020150]

Before concluding that you need an expensive new diff, try checking the endfloat of the diff output shafts. If it's more than 6 thou (sorry, an old money measurement) there's a reasonable chance the output bearings could be guilty of making the noises you are hearing. The output shaft bearings can be changed in situ, i.e. without removing the diff from the car, making the task a lot cheaper than a replacement diff. It will always be a gamble whether the rest of the diff is also noisy but if you do the work yourself, the bearings and seals can be found for about £30 or so a side. Mike.

[xrjohnny]

I had a diff whine at about 40 mph . I found that there was also play in what I at first though was the output bearings . After changing the oil for 80/140 to try to & reduce the noise. I discovered that what had happened was that due to previous heavy thrashings the crown wheel side diff carrier bearing has worn slightly thus losing the crown wheel carrier preload on the bearings. This allows the crown wheel to move away from the pinion thus causing whine. It also causes the output bearings to be loose in their housings being felt at the wheels. This play can be taken up by tightening the large castellated nut on the crown wheel side of the diff after first loosening the locking tab. A bit at a time. I tightened mine about 2-3 teeth ( 1/4 turn) this got rid of the diff whine & removes the play in the output bearings. I have now have no play at the wheels. Worth a try before you buy a new diff - easy to get to if you have some drive on ramps . My car xk8 had 58000 miles.

[Rocket3]

Thanks for the info. I'll have a look at that.

[xrjohnny]

Here is a picture of the output bearing retaining nut.