Bevel (angle ) gear oil R&R

[Ragman]

I'm sorry for dredging this up again but it's still not clear to me. Does the 2001 XC use 75W90 synthetic gear oil or 3309 ATF? Gibbons sugested in one post that this oil should NOT be replaced. Is this still true?

[BillAileo]

The Volvo bevel gears use synthetic 75W90 gear oil.

The following is a cut and paste of Gibbons' August comment on fluid changes:


"Hey Gome, I hear ya on changing fluids. But I only worry about some. My general rule of thumb is, if the parts roll in the fluid, I don't worry too much. If anything is sliding, then it's an issue. For example, a gearbox doesn't bother me because properly designed gear faces actually roll on each other, they don't slide, and bearings roll. So there really isn't anything going on in a gearbox to generate massive amounts of particles. Pistons slide in cylinders in motors, and clutch plates slide on each other in automatic transmissions. This sliding continually scrapes off little pieces that get go into a colloidal suspension in the fluid which then becomes an abrasive slurry. That's part of the reason you change oil, it is "dirty" with those little particles."

"Newly manufactured surfaces need to "break in" to each other by wearing off the imperfections, much more pronounced on sliding surfaces. And it all goes into the fluids. So it's nice to get it out."

"When I changed the ATF early on in my car, the thin layer of factory original fluid on the dipstick sure looked nice and clear. And it smelled OK. But when I put a quantity of it in a clear glass jar, it was a dark opaque mahogany color. What made it opaque? I have my paranoid suspicions...."

"So for me, change motor oil and transmission fluid, but don't change the bevel gear box oil or Haldex. Yes, the haldex has clutch plates, but they get used very, very little."

Notwithstanding these comments, I went ahead and replaced the bevel gear oil in our '03 at about 70,000 miles.


Bill

[Ragman]

Thanks Bill.