Jaguar Forum banner

1 - 20 of 41 Posts

·
Registered
Joined
·
53 Posts
Discussion Starter #1
Well as the title suggests. I’m hearing a dull knock sound when lightly accelerating and again on lift off. I don’t think it’s tank slap as it’s only seems audible at low speeds when only just touching the juice pedal, It seems to come from the rear end but can’t be 100%
I know it’s almost impossible to diagnose on a forum but just wanted to see if anyone else has this or if it’s normal? The car is a 2011 Xfr with 70k
Cheers stu
 

·
Registered
Joined
·
3,503 Posts
Can you tell where the sound is coming from?
Front, rear, inside, outside, boot, engine bay etc etc?
If it's from the front/engine bay then my prime suspect would be the coupler/torsion isolator inside the supercharger snout.
 

·
Registered
Joined
·
53 Posts
Discussion Starter #3
Thanks for the reply. It sounds like it’s from the rear of the car but understand how deceiving sound travel can be. My son did say it sounds like it’s behind the glove box so will investigate further tomorrow. It almost sounds like there is play in the gears or drive shaft or something as there is a slight delay from accelerating to the noise occurring ,the car drives perfectly otherwise.
 

·
Registered
Joined
·
4,414 Posts
First it’s not normal, my XFR is silent on light or heavy throttle. I’d have a look at the drop links on the rear suspension as I’ve had one fail. Just jack it up and give them a pull to see if there is any loose movement. If it is them they are not expensive parts!
 

·
Registered
Joined
·
53 Posts
Discussion Starter #5
Yeh I’ll give that a go , thanks for your input hopefully it’s something as simple as that!
 

·
Registered
Joined
·
53 Posts
Discussion Starter #6
Well I took my car to a local garage and they got it up on the lift so I could have a good look at The the drop links etc, everything seems normal . Gave everything a good push and pull so see if there was anything worn but all seems fine. However I did notice the n/s diff casing was a bit damp with oil! Didn’t look fresh but a little worrying
So I’ve started to wonder if this knock sound is the start of an issue with the diff?
On a more optimistic tip, could the noise be the exhaust valves opening and closing? It has a long life exhaust system fitted which came with the car when purchased, sounds great when giving it some beans so maybe I’ll have to drive it with a lead foot so I can’t hear this annoying knock sound lol 😂
 

·
Registered
Joined
·
6,476 Posts
What about the handbrake. That gives a bit of a thump when releasing. Also my rear brakes can make noises when releasing off the foot brake in traffic that sound a bit like a thump.
It is a noise that you know comes from the rear though...


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
484 Posts
Did you check the Diff' oil level? Also, a knock like that could be a little play on the Diff' gears or Prop' U/Js.
 

·
Registered
Joined
·
53 Posts
Discussion Starter #9
No I didn’t check the level. Tbh the fella just wanted to go home and wasn’t overly interested which is why I got under myself and had a look. How do you check diff oil levels? Is it an easy job? Also if it’s play in the diff or driveshafts would that mean replacing or recon ? Many thanks
 

·
Registered
Joined
·
3,503 Posts
No I didn’t check the level. Tbh the fella just wanted to go home and wasn’t overly interested which is why I got under myself and had a look. How do you check diff oil levels? Is it an easy job? Also if it’s play in the diff or driveshafts would that mean replacing or recon ? Many thanks
If you haven't already, get yourself a copy of the 2010-2011 XFR Workshop Manual from my Dropbox here: https://www.dropbox.com/s/bet26xniuafluyn/2010XFRWorkshop.pdf?dl=0
Then go to page 528 to start reading up about the e-diff on your XFR.
The fluid drain and refill procedure is on pages 539 and 540.
It doesn't explain how to check the diff fluid level though, all it says is the fluid capacity is 1.3 litres and NOT to fill the diff up to the level of the fill plug as that is not the "full" marker.
It looks like the only way to be sure is to fully drain the diff then refill with 1.3 litres of fresh fluid, and on a seven year old car that is probably due by now anyway.
The other main tip I can give, based on my memory of reading about this on other forums, is that the fill plug can be a PITA to access and remove so make sure you can do so BEFORE you remove the drain plug.
The fill plug is on the side of the diff and the drain plug is on the bottom of the diff.
 

·
Registered
Joined
·
53 Posts
Discussion Starter #11
Nice one for the info! I think that’s where I’ll start. Will probably take it to a local jag place to get it done due to lack of space where I live. Thanks again!
 

·
Registered
Joined
·
236 Posts
I had the same as this on my XKR. It was the diff itself. Not sure if I've got the exact fixings right, but the problem was the diff had been off by previous owner and they hadn't put washers back on - just bolts through the diff to the chassis. The bolts were then bottoming on the other side of the box section and appeared tight but the diff was moving slightly creating the "clunk" noise. My mechanic removed each bolt one at a time and cut a couple of mill off the end and replaced. Problem sorted.
 

·
Registered
Joined
·
236 Posts
Very interesting! Are the bolts that secure the diff easy to see when on a ramp?
Yes, very easy. I was down in the pit with the mechanic and he showed me the problem. Worth a look, I went a whole road trip to Europe with the problem, it's a wonder it didn't snap the bolts!
 

·
Registered
Joined
·
53 Posts
Discussion Starter #16
Just an update. Took my jag to a local specialist who reckons it’s either diff or prop shaft related . I’m going to book it in for some ramp time for diagnosis and see what the outcome is.
 

·
Registered
Joined
·
53 Posts
Discussion Starter #18
Well sort of. It’s currently in a jag indie having all the rear bushes/ arms replaced and shock mounts/ bearings . After a little investigation the diff and prop shaft were ruled out. The car has a warranty so hoping they will pay for the works but they will probably play the wear and tear card.

Whilst the car is in pieces I’m gonna get him to change the diff oil for good measure
So hopefully returns without the knock.
 

·
Registered
Joined
·
10 Posts
I was under mine at the weekend manipulating the drive-train to try and figure out where the slight clunk was coming from. Wheels up and neutral engaged I couldn't feel any slack in the propshaft or in the driveshafts going into the hubs.

I could hold the propshaft and move the wheels backwards and forwards about 15mm (about 2 degrees) without the propshaft moving, but this isn't a large amount when you consider the diff was cold and there would need to be some allowance for expansion as well as a little gear wear after 90k.

I'm starting to suspect something suspension/linkage related, and look forward to hearing if there was anything in particular the mechanic spotted worn as he looked at your car.
 

·
Registered
Joined
·
53 Posts
Discussion Starter #20
I was under mine at the weekend manipulating the drive-train to try and figure out where the slight clunk was coming from. Wheels up and neutral engaged I couldn't feel any slack in the propshaft or in the driveshafts going into the hubs.

I could hold the propshaft and move the wheels backwards and forwards about 15mm (about 2 degrees) without the propshaft moving, but this isn't a large amount when you consider the diff was cold and there would need to be some allowance for expansion as well as a little gear wear after 90k.

I'm starting to suspect something suspension/linkage related, and look forward to hearing if there was anything in particular the mechanic spotted worn as he looked at your car.

Im picking the car up on Friday so will keep you posted! As far as I’m aware it needed pretty much new everything at the rear, upper lower arm etc! Warranty backed out ( what a surprise) so I’m picking up the bill, still waiting for the final price 😭
 
1 - 20 of 41 Posts
Top