Differential
The Differential fitted to the Rover P6 is robust and as long as the oil level is maintained there should be very few problems to deal with. The most often cause of irritation is leaks. This is usually due to the breather becomming blocked, as pressure builds up the drive shaft seals fail. Later cars did away with the breather. The filler position was also moved from the rear of the case to the right hand side. This later position makes filling infinatley easier.
The oil should be changed every 24,000 miles using a good quality EP90 grade oil.