I recently started to notice a thud from the rear. Might even call it a clunk. I thought it might be a loose spare wheel in the boot but it's definitely not. Unfortunately.

I can trigger the sound by lifting the foot off the throttle and then tap the throttle again while driving . it's from the rear right side coming from the tire or axle area.

I fear a costly repair. . Any ideas?

I have not yet checked the diff as I've only had the car since September. It's got 85000 miles (138000km) and it's a 94/95 4.0 sovereign.

 

Loose wheel nuts?
worn driveshaft joint? They need greased regularly, and can fail if it isn't done. For what it's worth, that seems quite a low mileage for a diff to fail at, unless it has an oil leak....
A frame bushes?
i am basing this on your description of the noise being towards the louder end of the spectrum and drive related rather than bump related. There are plenty of other bushes and of course the shocks, but everything is doable at relatively reasonable cost, except as you have surmised, the diff. As I say, at your mileage and absent an oil leak, it seems less likely. Fingers crossed!

 

As you define the clunk vs. rumble for others input will help define it , the Differential is not bad on cost of parts and labor skill level if you do it yourself . Have some tips on your Diff. as you define exactly where it is .

 

I do actually only have 4 out of 5 wheel nuts attached as the 5th stud is not original and the threads are worn. But I can't imagine that making such a thumping sound, and with 4 out of 5 studs in place it really shouldn't be able to move I guess??

I have not checked the driveshaft joint but it sounds like a good suggestion. The car has low milage but it's been neglected for the last 10 years. I recently read on the x308 forum that issues with a torque converter caused a similar thumping sound when you tap the throttle on/off but as it's only coming from the right side if the car it's more likely with the driveshaft. I just changed the transmission oil as well.

Rear a frame bushes was also changed a few weeks ago to poly bushes from powerflex.

I will inspect the diff tonight. And like you say Countyjag; fingers crossed.


and "lady penelope" thanks for the input but what do you mean exactly with Have some tips on your diff" ? Sorry but I don't think I understood?

 

If it comes down to the differential bearings I have some do it yourself repair suggestions . I use to replace bearings like this on jet engines . If it comes down to the differential . Keep getting suggestions from others as you hunt down the cause of the sound . 4 of 5 wheel studs is not a safe practice as it puts a strain on the remaining 4 and could fail in a bad consequence . Better safe then sorry

 

I see! Thank you. I will definitely have to figure what this sound is. And the 5th stud is scheduled for repair very soon.
Took it to work today. I didn't capture the sound on this video though but I might give a try later.

 

Tcasmarcus,
Is there a back story here? Was anything else changed when the A frame bushes were changed? Was the noise audible before they were changed? Have you checked that everything which was loosened off to remove the A frame (and any other work) has been tightened? Im sure they will have been, but when faults appear in areas where work has recently been performed....
I agree with Lady P re the wheel nut, but doubt that it is causing this particular problem unless they are loose.
On the basis that sounds can be misleading to trace back to their origin, have a look at the propshaft couplings as another potential source of drive related noise.
Is there any play when you have the wheel jacked up off of the ground? The lower part of the hub at the rear pivots on some tapered bearings which can wear allowing for some play. Easy enough to replace, but the pivot pin sets the alignment at the rear, so it would need reset if you have to make a change.

 

I jacked the car up and tried to pull the tyre in all directions but there was no play in any bearings. It felt tight. I had a look around but couldn't see or hear anything obvious. I did manage to find a 5th nut though that fitted the damaged stud so now all 5 are Ok.

Went for a drive and during the first 10 minutes I actually thought the problem was solved, but as I kept on driving it appeared again. It's a thump. You kind of feel it in your back through the seat. And when I increase the speed and pass 100km/h it feels even more violent. I tried to film and record the sound but even though you can hear the thump it's the sensation of this thump in the back that is really annoying.

I could not see anything lose connected with the a frame bushings but I might take the car back to that garage and ask for help if I don't figure it out.
I'm puzzled. . I do think the sound was there before I changed the bushings.

Perhaps also worth mentioning is that I hear a high pitched whine from the transmission when I go slow and it changes from 1st to second gear. Hard to describe that sound unfortunately. Not sure if it's related.

Here is the "thump " :

 

Have you had a look at the rear engine mount, to give it its correct name? I always think of it as a gearbox mounting, as it is at the rear of the transmission. There is a spring mounting, which you can move with your hand by what always strikes me as an alarming amount. There is a foam bushing, a bit like the material the rear shock top mounts are made of, which damps the movement of the gearbox and stops it making a noise. Your noise sounds very like it, and the thump in the back of your seat is almost exactly that; the bush is in the transmission tunnel right in line with the rear of your front seat rails. A fairly common fault.
If it is the foam bush, it is an easy and cheap fix.

 

Could also be the exhaust hitting something, the space is tight in there.

 

Good suggestions here.. I hope it's either rear engine mount or exhaust but honestly it sounds like the noise is further back even though the sensation of the thump can be felt through the seat. I think I'll try to change the diff oil within the next few days and have a proper look underneath. But unless i see something obvious I guess I'll have to take it to the garage and throw my money at them.

 

"the sensation of the thump can be felt through the seat"

I'm just guessing, but I'm going to say rear upper shock mounts.





Stu

 

I actually started to think the same ,Stu! But when driving over speedbumps etc I'm not sure if the sound is there.. but I will definitely also have a look at the shocks

 

I had a clunk from my rear end, turned out to be worn inner wishbone bushes, not detectable by grabbing the wheel, but seen by prising when on a lift. Quite a job to replace, I ended up swapping the complete rear end as a unit instead.
I still have the original which I intend to rebuild with all new bushes and bearings, although it is well down the list!

 

Just returned from the garage. They took it for a drive and heard the noise. They are not jaguar specialists but good mechanics so they've been helpful so far. They've also worked on the car previously, doing the a frame bushings and some other stuff.
They jacked up the car and I gave them some ideas that has been mentioned here by you guys. There was no noise from the exhaust, all bushings seemed tight and the were no play or noise from the shock mounts or engine mounts.

The u joints looked like they had never been greased though so the mechanic thought that might be the reason. He injected grease on all the nipples. I took it for a test drive but it didn't help. There might have been a slight improvement but it's still there. So we basically don't know what's up. He said it might be some wear in the driveshaft.

not sure where to go from here.. maybe it's not worth following up at the moment as the cause is not clear?Maybe wait till its a bigger problem?

 

Are you sure they checked the correct ( rear) engine mount? It has about 2 inches of play in it when it is in good working order, and it is quite disconcerting to see the tail of the gearbox wafting about. It is almost in line with the rear of the drivers seat rail.

 

No, not really sure. They examined the car rather quickly. But as they actually did it for free, I can't really complain. I plan to change the diff oil very soon at that garage. Maybe I could ask them to check more thoroughly then...

 

If you are able to get under the car safely, it is easy to check yourself. You will be able to move the rear of the gearbox and propshaft, and will hear any noise. The fact you feel the thump in the back of your seat strikes me as an important clue. And remember, it is an easy and cheap fix!

 

Damn.. I was under the car yesterday as I rented a local garage to change the transmission oil. Didn't think about moving the tranny about, unfortunately.

I'll check the next time

 

I called one of the jaguar experts over here and explained the problem. He thought it might be a hub carrier bearing and told me to start the car, and with one foot on the brake, change between D and R and listen for any clanking noise. I tried to film while changing between P D and R and there is a noise although it's not filmed from the best angle and position.

He said if not the bearing it might be the diff. A lot more complicated and expensive. I will anyway try to change the diff oil but I can't seem to find the information regarding the mm tool needed for the drain plug and which tool to use to open the fill hole.

I have also started to consider the a frame poly bushes again after reading aTB . Didn't manage to attach the file but here is the screenshot of page 1.