My XJ8 vibrates. Mechanic who used to work for Jaguar told me that I need new rear flex joint. But I can't find the part anywhere. Dealer wants to sell whole drive shaft which cost over $1500 instead of $100 flex disc. I see the flex disc made for 2003 and under. I was wondering where I can find the flex joint for 2004 model. Is this part different than 2003 model part?

Noori. Have you talked to these folks?
May have the answer.
Good luck.

how do you know if the flex joint is bad? Just curious.

It might be helpful in your searches to know that it is known as a "jurid coupling"

The search for jurid jaguar on ebay.co.uk leads to this for the X308:

Jaguar X308 XJ8 XJR Prop Shaft Flexible Jurid Coupling | eBay

About $30, give or take.

The best bet for aftermarket is often the UK based suppliers. Keep in mind that the term used in the UK is "propellor shaft".

If a X308 coupling is not a direct fit, perhaps a driveshaft shop could modify a X350 driveshaft to accept the coupling.

My mechanic used to work for Jaugar. And he said it always is flex joint problem. I think it would be easier place to start than taking whole drive shaft down.

That rubber coupling for the X308 looks suspiciously like the one in the picture of the driveshaft in my technical notes of 2003.5 for the X350 car. Only way to find out is to buy one and compare. It's called a Jurid Coupling BTW. I can't believe Jaguar would go to all the time and trouble of using something different, but I may be wrong.