I have a 98 with over 220K. I've never changed the bevel gear oil and often tow a trailer. Re: Oil leak, the most common is the turbo oil return line. On the XC it's tricky to reach, you have to bend a cooling line slightly and you're mostly working blind. Get an extra seal in case yours goes in crooked. It would help to look at a fwd model closely before doing your XC - the fwd's are easy.

Ryan,

Follow the rear driveshaft (aka propshaft) to the transmission, the bevel gear housing is the exit point on the transmission where the rear driveshaft leaves the transmission. There is no drain on this unit -- some folks do drill and tap one in -- but standard drain & refill is done by loosening unit, replace seal, and then refill.

Turbo bearings are water cooled from engine coolant and lubed with engine oil, sounds like you have the classic and common oil return line weeping oil. Head over to Volvospeed.com and check out http://volvospeed.com/maintence.htm (aka Bay 13).

For the bevel gear: http://home.ripway.com/2005-4/294125/Volvo/V70XCBevelGear.pdf

Search the forums for xc70 problems to make sure you do everything to preserve the health of the 4wd system. It is a little fussy if you don't maintain it well.

Your car has a low pressure turbo, i think. As for the T5 it is a floating hydraulic bearing type turbo, using engine oil for lubrication. The leak is probably where the oil return line connects to the oil pan. You simply have to change the o-ring.

good luck