Hello everyone!
So we have a 2003 Xj6 with 90k kilometres on board (+ - 60 000 miles)
The car was sitting for a while after i bought it with a defect which is becoming anoying because it seems like i'm running out of ideas where to look next. I'm drom Ukraine, we don't really have good Jaguar mechanics so i wonder if anybody could help with where to look next.

Between 50 to 90 mph the car is having a slight vibration that is coming drom the rear. Seats and console start to vibrate (especially the rear ones its like a massage). Vibration is accompanied by a slight humming noise. I can also feel it fron the start while doing 0-60 and the engine RPM's are over 3000

All tyres are new Michelin Primacy (year 2021)
Alloys ablsolutely straight
Prop shaft was removed and diagnosed/balanced on a special stand. (All the parts are intact, including u joints, center bearing and etc
No play in suspension bushings
I did see someone has been in the rear diff as it has non factory sealant

Looks like someone was trying to resolve the problem but never succeded.
The car is all original paint and never been in an accident
Really asking for you help guys. I like the car a lot i don't have a clue where to look next
Maybe 2003 model year beeing the most early one had transmission defects that i should look after?
Never found this in google.

Any advice would be really helpfull! Thank you in advance

 

You don't mention wheel balancing. Obviously this was done when the Michelin Primacy tyres were fitted, but it might be prudent to check if the balance weights are still all there. The other thing to mention is the flexible coupling between prop shaft and diff. These are a known failure item, although I would not expect it a the kms you mention.
Other thing to check is the gear box mounting, and also the wheel bearings. Also sometimes the exhaust system mounts can fail and pass vibration into the car.

Hope you win the war, BTW !!!

 

Check the engine/ transmission mounts for play.

 

I have a 2003 xj8 with 347000km
My first thought is the new tyres and wheel ballance, next your brake discs ,then bearings then the differential
get the wheels balanced again but at a different shop and change your diff fluid directely after driving, costs a penny.
Diff of 2,7tdvi ,3,0 v6 and 3,6 v8 are the same . The diff of 4,2 Na xjr superv8 are the same

 

Yes the engie /transmission mount is important if you have a clunk while driving and a huge differece uphill then downhill. When the transmission gearbox is moving backward or forward due to play

 

From Robert rawle the vibration you are talking about the rear differential is that the tail sticking out of the diff goes in the propshaft is out of balance I used to work for Ford motor company in Swansea plant south wales UK I was on the launch and prototype of this axle its the x202 x350 differential we new from jaguar that there was problem with vibration they could not find the problem I was on assembly of the axle then a little later I went on machining of the crown wheel and pinion I was machining them after the heat treatment I was the one responsible for the quality I noticed that the tail stock sometimes was out a few microns I used to bang the pinion on the little end to straight it and check on the marposs quage it was right when I finished them and the crown wheel they were still getting the problem vibration me and Ian Davies the engineer found out what the problem was he was whatching me machining and noticed how I was getting the pinion in speck we talked and asked me how I was doing it then we went through assembly and realised it was getting out of speck buy taps on assembly in the end we put hand gauges on each axle diff buy flange the bit sticking out the pinion turn it with the gauge on when out of speck on the high point tap it with a soft hammer check and see if it comes in speck if not try again until in tolerance the amount of tolerance you got to play with is 5 to 10 microns then no vibration I was the one who solved the problem let me know if that works from Robert rawle

 

It's not the wheel balance. Wheel balance may cause vibration (mainly on the steering wheel) however in my case it's accompanied with heavy humming noise from the rear (it sounds like all 4 wheel bearings are dead). It's not the prop shaft, it's not the diff (we took it apart, it's like new inside) nor it's the engine,transmission mounts because the vibration and noise are coming from the rear end of the car. Robert Edwin rawle tangerinedream1 thank you for your post, my next step will be looking after for that

 

I hope this will work for you I got a 2005 xjr x350 2005 the diff is a 2.87da the diesel diff is a 3.07ea and the 3 litre and 3.5cc is a fa

 

Issue solved. The problem was a faulty propeller shaft, which was misdiagnosed previosly by certain "professionals". After relpacement, the car now runs smooth as butter. Thanks everyone!

 

OK great I hope what I said is the problem good luck from Robert rawle