My XK8 is the 2005 4.2s version and I have noticed that when accelerating hard from standstill (or nearly so) there is a strange very short noise from the rear which I can only describe as an "oink". Perhaps it's something to do with the electronics controlling excess power to the rear wheels. Is that possible? Has anyone experienced similar noises and if so, any idea what it is?
Ray

 

Maybe a whoop? Search the forum for bark or whoop noise and see if what others describe sounds like what you hear. If so, lots of good info here on the forum.

 

You're hearing the classic 6-speed ZF "bark". After the transmission fluid gets a little age on it, the clutch packs tend to grab for just a split second on certain upshifts. When they do, you hear the "bark". I have spoken with ZF tech support several times about it. They claim it is simply an annoyance with no damage being done to any of the ZF's internal components. The remedy is essentially fresh transmission fluid (a drain-and-fill). Depending upon your mileage, you may want to wait awhile. ZF claims that under normal driving conditions (a 50/50 mix of highway/city driving, no towing, no dirt or gravel roads, and no hot-rodding), the Lifeguard 6 transmission fluid is good for 100,000 miles. But most of us long-time forum members will change it prior to that....

 

Thanks Jon for that explanation. At 53000 miles I think I will wait awhile before changing the fluids.

 

Our S-Type is pushing 75,000 miles. Our XK8 is pushing 60,000 miles. Both have barked occasionally, mostly during our summer months. I never hear the bark during the autumn and winter months in our S-Type....

I plan to do drain-and-fills on both of these ZF units at 80,000 miles....

 

I had a pretty consistent bark which went away with a fluid change. I'm in Phoenix, where, by most standards, we don't really have autumn or winter, so it was a year round annoyance.

The indie I take the car to recommends doing the trans fluid and filter at 60k intervals.

 

I agree with the indie, 60K miles is a good time to do the change of fluid and filter. I changed mine about 50K in both cars but I am paranoid about fluid in a $6000 tranny. It's just cheap insurance, and it shifted like new after the change.

 

I have a 2000 XK8, it is breaking a bit faster than I can fix it. Today's episode is :

When hard accellerating, eg freeway on-ramp, when shifting into 4th or 5th, I have been hearing a loud clunk in the rear end, just once on the upshift. My car has 67,000 miles on it. I just bought it, no service records and I'm thinking about changing the J shifter tranny fluid right now. Does this sound particularly odd or is it consistent with these cars? I'll search the forum FAQ for recommended best fluid and how to perform the fluid change myself... Someone said IIRC gearbox oil, sounded expensive....

 

I was having the "bark" issue, but more noticeable was the infamous "lurch" that you would get shortly after coming to a complete halt... this started at about 42k miles. I replaced the filter/pan and put in new fluid, and the lurch and bark have completely disappeared.