Hi,

Just looking to confirm some information I’ve found on this site.

Have a US 2021 x3 m40i and want to change the rear diff fluid. If I’m not mistaken it takes .8l of BMW G5 hypoid axel fluid?

I believe I have the non-M diff as there are no fins on it and I did not find the option on the vin by using mdecoder.

I found a few other posts on this site but wanted confirmation.

Thanks!

FYI - I called the local dealer and they told me .9L but everything else I’ve found suggests .8L including these posts:

https://x3.xbimmers.com/forums/showthread.php?t=2029442

https://x3.xbimmers.com/forums/attachment.php?attachmentid=3243116&d=1690929572

Just looking to confirm actual capacity.

As long as it's less than 1L, it doesn't matter that much, as, like any other diff, you pump until it flows out the hole.

Just finished. G5 BMW gear oil. Sucked out most of it because I was able to get just over .8L back in. Barely trickled out.

Thanks for your input.

Stilhere wrote

Just finished. G5 BMW gear oil. Sucked out most of it because I was able to get just over .8L back in. Barely trickled out.

Thanks for your input.

Does it have a drain plug or you have to vacuum it out?

bbb83 wrote

Does it have a drain plug or you have to vacuum it out?

Vac. Used this:

https://a.co/d/ccuAaoe

In the UK they’re a non serviceable item, in fact BMW UK will void your warranty if you service the diff, which is ridiculous in my opinion.
You try and do the best for your very expensive vehicle by servicing it and the dealership screws you over for it!

Yeah they also say the transmission is non-serviceable. Call ZF and they will tell you to service it for sure.

Diffs and TX case are no different. Must service especially if you drive hard and use launch control often.

My diff oil (F&R) was ugly when I changed it at ~30k miles. Front diff gets incredibly hot. Took two hours to cool down enough to touch after driving to my buddy's shop.

Diffs are vented to atmosphere so they're not a sealed unit.