I don't believe that there are any special significant differences the front wheel mechanics of teh AWD versus teh FWD's. Engine and most mechanicals are same as the LPT FWD models. Body panels are the same except for the bumper shells. Interior is the same. Anti lock and traction are the same system. Biggest differences aside from teh actual AWD mechanicals seems to be the rear suspension, rear axle, etc. The rear axle is essentially from the V90 with its limited slip differential, so everything about it is different. Rear brakes are different, including parking brake shoes and cables. Parking brake cables are more prone to failure due to the tight radius turns of the cable back around teh suspension arms (FWD's run much straighter) and they are harder to replace. For some reason, many of the AWD's wear out rear brake pads at twice the rate of the fronts, but nothing special about replacing them.

Our '98 XC has 92k now, and the only repairs of note have been the air pump, the parking brake cables, and a water pump whose bearing failed after less than 25k miles (very unusual way for pump to fail). Otherwise, it has been one of teh most trouble free cars we have ever owned, and still gets frequent unsolicited praise from my wife, who has never made any positive comment on a car before this one. With snow tires, traction, locking rear diff and winter controls for transmission, it just about ignores snow conditions and is always poised and secure.
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Mike Sullivan ('95 855T (88k), '98 V70XC (92k), '95 855 NA (135k). Past Volvo's: '85 744 (256k), '86 245 (165k), '86 245 (195k), '88 745 (208k), '91 745 (196k), '93 965 (147k) .