Please correct me if I am wrong, it was my understanding that this was only an issue on the pre-06 S60r's. I read that the 06 and 07's had revised angle gears to correct this issue. I was looking at getting a S60r for a little while.
It's an issue with the pre 06 manual and automatic transmission cars and 06-07 manual cars. Also it's not the angle gear that's the source of trouble. It's a coupler gear made of soft metal that mates to the shaft of the angle gear. The coupler gear splines wear causing loss of awd and eventually may damage the shaft of the angle gear. The 06-07 automatics have a different angle (some call bevel) gear and a hardened coupler gear. There appears to be an XC90 diesel in Europe available with a manual transmission that has a hardened coupler. This is being investigated now as possible replacement.


