My RS6 experts, help me out with differential fluid questions:

Hello,

I have an issue with the first service on my M5. They replace the differential fluid at the first service and BMW does not have any! LOL.

The car calls for two different differential fluids in this car. I think the numbers are 83-22-2-413-511 HYPOID AXLE OIL G2 for the front and 83-22-2-447-362 HYPOID AXLE OIL G4 for the rear.

The M550ix uses the same fluid in both front and rear and as best I can tell it is a 75W90 fully synthetic GL5 gear oil.

This hypoid axle oil is listed on ECS as : Hypoid Axle Oil G4. I was able to find out more info on this rating and think it's G1, G2 and G3 are mineral based and G4 is a synthetic product. The G3 and G4 products were listed as the same weight 75W90, and the G1 and G2 are listed as 80W90 weight.

Some have had their service done and the dealers have done a few odd things at various locations. One did everything but the rear differential and did not tell the customer. One put the same fluid from the front in the rear, did not tell the customer, who then asked and was told BMW NA told them to do that. It's a DRC like screw up as far as I can tell.

So, my thought is that they should substitute the Special Super unavailable fluid with something that at least has the same weight, if not the full synthetic type as opposed to putting in the wrong weight. Then someday put the correct specification product in the rear differential when it is available. Comes from Jupiter Moon I think. Europa?

I know the first change is to get any manufacturing left over metal bits out of the differential and reportedly the fluid in there from the factory is just mineral oil????? Who knows for sure.

Mike

Not an expert, but my guess is they spec a better fluid for the rear diff because it's getting more of the abuse, especially in an M5. Similar to RS6 motor oil, the manufacturer had to spec for the worst-case. For the M5 diff, I would guess that would be running hot and hard for extended periods on a track. With that in mind, I would be ok with the "lesser" fluid temporarily, but I wouldn't track it and would try to avoid beating on it hard for extended periods until the right fluid came in.

I would definitely want to do the fluid change on time, since BMW clearly thinks you need to get that break-in fluid out of there.

Call Brian at BND and be done with it

Quote:

Originally Posted by DHall1

Call Brian at BND and be done with it

I emailed the BG products people. I have to reach out to BND too.

Thanks,

Mike