Have had this for a few weeks now. It might have started after the differential+ujoint replacement in the rear, but I'm not 100% sure. Any ideas of what it might be? Due to the nature of the sound, it is very hard to locate, could be in the engine bay or under my feet.

[youtube]2Fdj6Barwzs[/youtube]

 

I'm pretty sure that is the transmission 'bark' which is a known issue on the 6 speed ZF. There used to be an additive to cure it, but it is out of production. Now the soultion is a transmission fluid change. The new fluid contain the correct additive already.

 

I am planning to do a fluid change sometime around next month. Lets hope it will cure it.

 

Steve - I don't think it is. The 'bark' is well named - a short noise on 3-4 gear change and mine was cured by new juices.
We don't know how many miles OP has done but that sounds more like a bearing/gear whine.
Azeteg - have you gone into 'Sport' mode and held gears to see if it is gear ratio related?

 

I think I did hear the "bark" right when he accelerated. The constant whine you hear after that sounds like the normal supercharged noise.

Doug

 

That is exactly the sound I meant. The whine is indeed just a regular supercharger sound, which I believe is in order. Changed the supercharger oil 2 days ago, so it should be all nice and fresh in there now

 

I'm surprised that the "tranny bark" is now just appearing in your car. Has this always been present since you've owned the car? I will say it is more pronounced in warmer weather.

 

My XJR does the same thing, it's a funny sound when it kicks down, like a whoop or a muffled shriek. I thought it was a slipping belt, but it's not.

It does it kicking down into any gear when the revs suddenly jump to >4500rpm and I was lead to believe that it's the sound from the lobes in the supercharger rapidly accellerating as it spins up...

The lobes spin at something like 12'000-13'000rpm, there is probably some transsonic or supersonic effects...

I dunno....

You're not talking about the "click" when you put your foot down, that's the sound of the pedal hitting the end-stop and the throttle body opening & hitting the stop. My old Ford used to make the click sound too....

 

Yep, missed it, need my ears cleaning out.
Just before 'there did you here it' - classic transmission bark.
Sorry Steve......
Change of fluid will sort it - and it isn't anything to worry about.
Cambo - yours is just that lovely supercharger noise.

 

Ah Steve that video i posted was a naturally aspirated 5.6L Ford V8, i just wanted to show the "click" which i thought i also heard in Martins vid. I guess we can go for a drive together on Sunday & have a listen...

 

Was that full throttle as it does not look quick for an xkr?

 

I think I floored it just to produce the bark, then let off slightly. It still is the swiss autobahn, so almost death penalty for speeding

 

When I started shopping for my Jaguar I test drove a 2003 XKR and forced a kickdown without actually flooring the pedal just to see how responsive the car was. Naturally I heard the bark/whoomp and pointed it out to the dealer that was selling the car. It was not a Jaguar dealer but a small exotic car dealership that happened to be next to a Jaguar dealership. Anyway the guy told me this was something that could be easily taken care of by the Jaguar folks next door.

I ended up not buying the car at that time but did do some googling to see if this was a well-known problem and found a bunch of posts on this topic. I think there is even a TSB and the solution was draining the trans fluid and replacing with fluid that had some additive. It is really more of an annoyance than a real problem.

Doug

 

I just listened to it again on a decent set of speakers, mine does sound the same on kickdown....so either my trans fluid needs changing too or it's normal...

Probably the former, since it's >90'000mi on the original fluid...

 

We could always compare the sounds tomorrow, mine is 97k miles, afaik on original fluid...

Dave Roche @ XK8 Parts sells a nicely priced oil+filter kit for the ZF6hp26 - 148 GBP. I was thinking about getting this one. Don't know if I'm up for the messy job myself however, I'd rather go to someone that has a lift, and access to WDS for transmission temperature reading...

Automatic Transmissions | Jaguar XK8 and XKR Parts and Accessories

 

+1 on the lift.
I used Dave's kit and it was £20 to get it here using Home - MD Couriers
I've got some stick on temperature sensitive labels which worked well.
The hard bit is undoing the undersized Torx screws. Be sure to order at least 10 of the bigger size from Dave.
Make sure you can undo the fill plug before you start!
The easiest way to start stubborn screws is with a small cold chisel + hammer.

 

My preferred method would be to spray the screws with penetrating oil a day before, then just before removal, give each screw a spray of electronics freezing spray, which should cool it down to -35c, hopefully contracting it enough to make it come loose without too much of a fight.

I just ordered some other parts from Dave (brake discs, pads, floor mats), and the shipping was a whopping 100 EUR, probably because the planet-sized discs for the XKR are quite heavy. Fortunately I save some on VAT, living outside of the Evil Union.

 

Then use the cold chisel!
Problem is you've got steel bolts in aluminium and the ally will contract more than the steel.
If it works I'd be interested to know but to break the electrolytic corrosion probably needs a shock.

 

The latest xk8-parts kit includes everthing you should need, including 21 of the new size screws.

 

One of the threads related to the "bark" has a response from ZF, the tranny manufacturer, who explained that the noise is harmless and is what they called the clutch plates humming and it is not a sign of impeding transmission failure. Of course, a fluid change couldn't hurt. I will be changing mine in the Fall. In the meantime, I must admit I sorta like the sound. It's like the car is excited by being pushed hard. Whoop!