XJ6 rear suspension conversion from leaf springs,who has done it?
The Series 1 XJ6 has that wonderful independent rear suspension with the lower wishbone and fixed-length driveshafts. Mine is starting to sag and the bushings are shot. I can either rebuild the factory setup or look at upgrading while it's apart. Has anyone fitted polyurethane bushings in the rear end? And is the ride quality trade-off worth it for a car that's primarily a comfortable tourer?
The XJ6 rear suspension is a masterpiece of engineering and I would strongly recommend rebuilding it with OEM-specification rubber bushings rather than polyurethane. The poly bushings transmit more noise and vibration into the cabin, which defeats the purpose of the XJ6's famous ride quality. Good rubber bushings from SNG Barratt or XK Engineering are about $300 for the complete set. The subframe mounts should be replaced at the same time. A properly rebuilt standard rear end on an XJ6 is magic.
I'll echo JagLady's advice. The Jaguar IRS was designed around rubber bushings and the whole system works as an integrated unit. Polyurethane makes the car feel sharper but you lose the refinement that makes a Jaguar a Jaguar. For a Series 1 XJ6 that you're using as a tourer, keep it standard. Save the poly for a race car.