I mentioned this in another thread but I thought there was a significant enough information around my adventures in chasing a nasty noise that there may be some value in a separate thread.

Since I have owned the car I have had an issue that from a standing stop, if I accelerate quickly there was a significant knocking noise. I could avoid the noise if I would go easy on the accelerator until about 10mph and then I could accelerate as hard as I wanted. Problem was worse on hills or with more people in car. It actually sounded to me originally as valve knock. But - moving from 87 to 89 to 91 octane had zero affect. Couple cans of 104+ in the fuel, no affect.

Had the car on a hoist, tried to find a loose shield, exhaust, anything. Wrapped rags around the tailpipes, nothing. Lived with it for many months. Found if I heard it starting I could back off the accelerator a little it would stop. Accelerate slowly became my habit. Steep hills were harder. Sometimes got very loud - thinking almost jackhammer type noise (maybe a little dramatic but close).

Finally dropped the driveshaft and had a local shop that specializes in drive shafts look at it. Externally everything looked good. U-Joints weren't sloppy, flex joint looked good, etc.

Apparently, in an effort at maximum smoothness Jaguar utilized a tube in tube construction on one half of the shaft. There are internal rubber isolators that had basically given up the ghost long ago. Could have fixed it stock, but the shop basically suggested cutting off the tube on tube assembly and replacing it with a more traditional drive shaft. They also said it is near impossible for them to properly balance the tube in tube designs as they shift slightly under load, even if performing as factory.

While we had the shaft out, I knew the rear brakes were getting down there so we dropped the whole rear end, put in new rotors, calipers, lines, etc.

Anyway - here are the pics of the re-worked shaft. You can see the old tube in tube piece off on the edge. Re-used the original yoke, etc., but you can see much smaller and lighter setup. A lot more room under the car now (should have taken pics when up on the hoist but forgot).

Results? Couldn't be happier. No noise at all, and I even think the weight savings (think 5-8lbs was about right) resulted in better acceleration overall.

So if you have a mysterious banging noise on initial acceleration that cannot be found - at least one good suspect would be the internal components on an unnecessarily complicated shaft design.

Oh - and the newly adjusted, lubricated parking brake is a true joy. The effort to pull the handle is at least 1/2 of what it was and the car holds much better on a hill without have to tug, tug, tug, to get that final pinch on the calipers. Easy pull and its rock solid.

Thanks!

 

Super!!!


My lump has a simple old tech one piece drive shaft. It does just fine.


Carl

 

Glad you found it! Good excuse to get your rear brakes sorted out for the next 100K.

Curious, how many miles do you have on your car?

 

97k. Still had a little bit left on the pads but they looked pretty thin.

Original CA car. I am 2nd owner. Picked it up at the same address the original bill of sale was filled out with which was about 7 miles from my house.

 

Good Job, Mark!!
And, I'm glad for you that you got your rear brakes done at the same time. As infrequently as they're actually applied, you should Never have to do that again!
(';')