I’ve owned two XJ8s in the last two years (1998 and 2001).

I went to view an XJR, and I noticed subtle differences.

1. The dials were slightly different. Maybe all XJRs are the same?
2. The rear aerial was shorter and did not retract when the car was off - perhaps a sticky motor.

The tensioners have been updated to the latest.

Is there anything else that’s different to the later models?

 

The engine and management are updated on the later cars. Plenty of options added too. Early XJR had a 2 tone dash. Nothing visually added.

 

Other differences, in decreasing order of my certainty about them:

1. The front brake rotors are smaller on a '98 XJR than later models. Sellers usually lump all 98-03 XJR's together, but they're wrong. The 98's are smaller, 305mm vs 325. Jaguar may have changed them to 325mm sometime during the 98 model year, but the early ones were 305mm. Different calipers, different pads.
2. The early 98's used an extremely dark brown wood for the interior, unique to the 98's, making them cooler than later models. I may be biased about that. Haha
3. The clock face is different than later models.
4. The security system is 315 mhz vs 433mhz, so the antenna built into the rear window is different. The 315 mhz system may have been used a little longer than 1998, I'm not sure.
5. There are differences in the radio and sound system, but I'm not positive that it was unique to the XJR or the 98 model year in general. The 98 had no security code for the radio, so modifying the system is simpler. The 98 used Harmon Kardon speakers, while later ones used Alpine I believe.
6. I don't know when Jaguar started using the donut spare tires, but the 98 has a full size spare with the same rim as the other four. Accompanying this difference is that there is a small bulge in the carpet floor to accommodate the wheel size. Later models had a flat trunk floor.
7. You mentioned the rear aerial, but I think they are supposed to be the same on the 98 as all the other models.

 

The XJR front brake rotors change point was VIN 853935 / 6.

 

Unfortunately it seems to be very difficult to find replacement trim pieces because they are so much less common.

 

Brake pad is the same with 305 and 325 disc.