I am proud owner of 2000 V70R AWD that replaced an angle gear ($3,500) at 71,000 miles and am being told I need to replace it again at 71,500 miles. Volvo dealer says that this is because of the different tread depth on my tires, and gave me a copy of a 11/2000 Tech-Net Bulletin regarding tires on AWD Volvos. These bulletins are distributed on Volvo's intranet. He said that dealers were told to give this information to customers. I never received it. The bulletin says to replace "all four tires at the same time...always drive on tires of identical brand, size, construction (radial), tread pattern, load-, speed-, traction-, temperature-, and tread wear rating...failure to...may damage the transmission and all wheel drive system." Did anyone else get this information? The owners manual only says that tires should be of "the same size designation, type (radial) and preferably from the same manufacturer." Quite a difference in the two statements. Since Volvo didn't tell me about the "identical tire" requirement, I feel like they should replace the angle gear. Have any of you replaced your angle gear/viscous coupling? Should you have paid for it?