Garth, I bought my '99 V70 awd used with 46,000 mi. While crawling around underneath to inspect everything, I noticed a paper tag that was coming off of the sump like box that is bolted to the bottom of the Differential, or Bevel Gear box. Volvo calls it an "Oscillation Damper". It is a metal 5x7x1 inch sump like container full of oil apparently. The paper tag was glued on and the oil leaking from it soften'd it I quess. It's about 1" x 2" and has 2 bar codes on it. Below the upper code is P9445908 and 3,31 which is the part # and gear ratio. Written below the second barcode is T103232 and then AWD. The Dlr. tells me that they need that info to do a service on the oil inside..... Excuse me, I said, why is it paper and why is it gluded on if it's so important ?? The reply was "I don't know..." nice huh, Tom

If it's been damaged from different sized tires, it'll make noise and often when making a sharp turn such as doing tight 180 degree turns in a parking lot. It can also make noise driving it normally but only if severely damaged and if so, it's usually then so overheated that it's also leaking fluid, burning on the front exhaust pipe (nice huh?).

There is no drain plug from the factory so if you want the fluid changed, I'd advise having a dealer do it following the info in the TSB or TNN.

To do it, one lower case bolt is removed, then one drills through alluminum into the case until going into the fluid. One then needs to flush out the alluminum shavings, then re-fill the unit with a specified amount of a special type fluid (not just 75W gear lube).
The plug you're seeing is the filler plug and that's that, nothing else.