AWD Volvo's Angular Gear, Haldex and differential fluid LEVEL - strange instructions, don't you think?

[AVOIT17]

AWD Volvo's Angular Gear, Haldex and differential fluid LEVEL is determined in accordance with the instructions of Volvo in a manner that has always puzzled me.

All 3 units - after leveling the fluid with the leveling port hole - we are instructed to remove an additional amount: 100ml for the angle gear; 40ml for the Haldex Unit; and 50ml for the differential.

The first time I came across this information I thought "The engineers must of made a mistake when they initially determined the proper level of fluid". However this concept seem very unlikely - especially in 3 separate cases.

Also what I find rather strange is how little fluid we are asked to remove - especially in the case of the Haldex Unit at 40ml - which is about 2.7 Tablespoons!

Once I read that the fluid level at the port-hole is actually the right level but that there is (at that level) a propensity that some of the fluid may overflow through the vent hole. And since and if a drop of oil escaping on a brand new car may send a vehicle owner into panic mode - then Volvo would remove some of the fluid to be fully assured that such an event could not occur.

Years ago I thought a rear wheel bearings on a P3 XC70 were in need of replacement - BUT the noise I was hearing was actually from the rear differential. It was not loud, and many car owners might not of notice it - but I am rather sensitive to abnormal sounds. When discovering this I immediately opened the plug on the leveling port hole to check if the differential was low in fluid - it did not seem abnormally low. Since the differential bearing were a little noisy I decided to over-fill the differential. I put the car on a slight angle so that I could fill the case slightly above the level-port. At this point I figured I had nothing to loose since the differential was in need of being rebuilt or replaced.

That is when I learned that there was a lot of cases of the a P3 XC70 differential bearings going bad - a problem that can be an expensive to fix - especially if done by a Volvo dealer.

After overfilling the differential the car continue to make the same low pitch sound. I kept an ear out for when the problem would become worse and therefore when I would be forced to rebuilt or replace the unit. HOWEVER slowly the noise went quieter, until it completely disappeared. And I drove that car for a couple more years until I traded it in. For those years the differential worked perfectly and without any sign of bad bearings.

What I figured about the issued with these rear differential bearings is that taking out that 50ml is probably not a good Idea. Instead one should keep an eye on that differential level - as in check once a year - to make sure it is level with the port - as a preventive measure. That is what I have been doing with every Volvo I have owned since.

Anyway - does anyone has any interesting info about Leveling the fluid in these 3 units?

[jimmy57]

The levels they prescribe avoid any frothing of the lube that makes the oil escape through vent. I have never had AOC and diff vent oil when filled to fill hole overflow. I drive 85+ MPH in west Texas and on my 2010 XC60 it never had and signs of oil. The angle gears will have a little venting if full but I have only seen it happen o long high speed drives. It never reached the ground as it was minor. It was wetting of the angle gear case and a stain on splash pan. I have done several diff bearing replacements and never tried overfill to suppress or cure noise.