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Hey Vasara,

​​​​​I will suggest that to my mechanic. As for the tyre pressure i always keep at between 30 and 32psi which is what the door sticker suggests. I honestly don't know what else i should do, the only thing remaining is the front rear lower control arms bushes, do you think these affect the ride?

 

Hi DanielCh,

Tyre pressures: Ok, one more possible cause ticked over.
The lower suspension arm bush are rubber type. Flex from lowest point to uppest point somewhat near or less than 10 degree. Sure it´s rubber that make the flexing on these, there are no bearing etc what could seize. Basicly the more you drive, the less friction the rubber will provide. I don´t believe an rubber bush can cause your issue. Unless somebody have changed to the polythere bushes to your car? These don´t flex, they turn over the inner pin. In theory they can seize. (keeping mind about the forces involved, i would believe that they will have fast wear instead of seize.
Outer joint of the arm are an balljoint. I have seen these seized in "barn-long" standing still, but again the forces involved by vehicle mass are so high that seized baljoint turn very fast to very worn baljoint.
Btw: I am very sorry to ask obious (and maybe stupid) question. But have to check. Do you know the "Dynamic" button on centre console? The one with chekkered flag. Do you drive with Dynamic mode On? (red colour cheme on dials) In case you do, this will set the dampening on hard. (not so big effect on early 3.0 Diesels, where it only seems to effect how much vehicle will lean on fast corners) Again apologies if i ask obious.

 

Just to make it clear, the front lower control arms are two parts front and rear, the front ones were completely replaced with their bushes, and no one worked on the car before, all parts were original before replacing and my mechanic is getting genuine parts not aftermarket, so it's unlikely that another material was used for bushes. The rear part of the lower arms are still old. My car is 3.0 petrol not diesel, and i use the dynamic mode often and honestly i don't notice a difference, in both modes the car is not comfortable 😕

 

Ok, good.
Yes, on front axle, the low front "banana-arm" inner bushes are known to wear/soft quite fast. About 60-90t. I am in my 3rd set of these front/low arms at front axle, since i have 300t km (187t Mil) on the clock.
Ok, on petrol model you should feel noteble difference on damping between normal / dynamic mode. My one are diesel, where the tune are different for some reason what JLR never give out, and the difference are very small. However: The drive are smooth. Not as soft that S or 7-series, about same level than Panamera.
Not absolute sure, but it might be that the active damping system are learning type and stores the characters of each dampers? This could lead in mis-setting, specially when new parts are installed. Maybe old shocks were sensed soft and dampening have been turned harder and harder by body control module? <- Just quessing here. (service & repair manual don´t mention anything about stored settings)
Do you know anybody in your area who might have JLR SDD software? On that there are function "Full Vehicle Reset". This should reset all parameters, exept gearbox, what have its own memory and will reset only by its own part of the software. Since x351 have non-volative memory for settings just remowing battery(s) do not nessesary reset everything.

Just noted something from service & repair manual: "If there is an electrical power fault, or the ADM cannot control the dampers, they default to the firm condition" and: "The ADM receives its power supply via a relay and fuse in the CJB."
ADM means AdaptiveDynamicModule. That can sense errors and turn fault code On, but if it is without power, it might be that no other system check ADM is on-line, so no fault code at all. Please check that you don´t have blown fuse on Central Junction Box, located behind of rear seat midlle arm rest. -> I am now 82,6% positive that this is it !!

 

Which fuse number is that? I looked in the owners manual i didn't see any fuse in CJB that's related to ADM.

 

ENo idea. Service manual only mention fuse and relay in CJB, but no number... I did not found it from owner handbook, so again undocument fuse. (wery common on modern vehicles)
If you could get SDD connected on your vehicle, the system scan would show all modules detected or not. SDD might also point the correct fuse, when continue with sympthom based diagnostic forward with ADM module? -> It have been noted that even documentation points to the CJB for fuse location, the fuse been found on trunk, under lid lock cover or from rear fuse box, right side of the trunk. You could also try to seek blown fuse by using universal voltagemeter by measuring the resistance over to each fuse on the box. (fuses have small metal tabs on top for that purpose)

Edit:
Note: ADM are sitting right next to rear fuse box. The fuse are propably in rear fuse box. (and relay in CJB?)

 

Good day everyone, after a long time i drove my car again and really felt how uncomfortable and harsh it is, especially after driving other luxury and economy cars, all were more comfortable and softer than mine. So, I took it to a workshop where they scanned it on SDD. No codes related to suspension appeared. The mechanic suggested that the front shocks were replaced with non genuine parts and it is very common that when non genuine shocks are used the ride becomes super harsh. I mentioned that i think the tyres are made of harder rubber, he said yes tyres do affect the ride but to that extent, after he did a test drive and confirmed that it is abnormally harsh. What do you guys think?

 

DanielCh, I'm thinking you need to decide whether to put more time and money into this problem or sell the XJ and move onto one of those other softer riding cars you've been driving. With this much effort already into the car, do you feel like you want to throw some more cash one more time into buying the correct OEM front struts and also better tires that have been recommended on this thread? You certainly have the opinions and recommendations already from men who are really good experts on this forum.