Is the center differential on Volvo AWD a straight mechanical coupling, or something different?
I used to sell Audis back in 2004, and the Quattro in any model was strictly mechanical until a V6-TT came out with hypoid coupling (not sure what they use now). Anyway, the mechanical center had ZERO TOLERANCE for differences in REAL tire diameter, so if you had a tire with, say, 15k miles on it that was damaged beyond repair, you SHOULD replace ALL tires. Woe unto the person who wore out the fronts and just replaced them, because if the center diff wasnt gone yet, it would be. In short, the center diff's "brain" went crazy trying to accomodate the constant variance in tire diameters front to rear, or even 1 to 3. Result: EXPENSIVE replacement (as everything on an Audi - you thought Volvo was bad! LOL)
My understanding was that most competitors used a fluid coupling or something else, which had a little 'give' in tolerating front to rear variance. i really never even understood REAR differentials (all those gear just work by magic) but would love to hear any insight into what Volvo uses vs. what others (like, say Subaru) use.
Anyway, would anyone out there give some insignt into the center diff in my '02 XC-70 and vovos in general? especially variance in tire diameter, front to rear. I became acutely interested in this issue when i noticed my wife had let her cross country avoid rotation and now has over 1/32 variance fr:rr in tread.
BTW, back in the Audi days, i DID drive and demo some FAST audis. I sold several new '04 S4 V8s (about 350 hp) and 3 (yes THREE!) RS-6s! The RS-6 had a 450 hp twin-turbo V8 and only a few hundred got into the US -- at $92,000+ apiece! (a new salesman later totaled a 4th on a demo! LOL) Nevertheless, VERY difficult to work on.....on the S4 V8, you had to take off the front end sheetmetal to do anything to the engine.)