Differential oil change - sourcing materials

DMike · Post by **DMike** » Sun Sep 12, 2021 11:03 am

Hi,
Getting ready to put the zed, a 2005 3.0i auto, on lifts and hibernate for the winter. In addition to the usual maintenance, this time I’m planning to change the differential oils as well - the oil is still from factory. Never done differentials before and after the bavauto’s video and TIS I still would need some advice from those in the know:

Drain and filler plugs, is there any way to know in advance whether they are the sealing ring or the O-ring type? Yea or nay for those magnetic plugs?

TIS says ”only change oil when rear differential is at normal operating temperature”, but never seen this mentioned elsewhere. Opinions?

Castrol Transmax Axle Long Life 75W-90 is readily available, is 1 litre enough?

Zulu4 · Post by **Zulu4** » Sun Sep 12, 2021 12:23 pm

DMike wrote: ↑Sun Sep 12, 2021 11:03 am
Castrol Transmax Axle Long Life 75W-90 is readily available, is 1 litre enough?

Did mine the other day, it took about 1.2 litres to refill.

colb · Post by **colb** » Sun Sep 12, 2021 5:02 pm

They have alloy sealing washers which corrode to lace so ensure you have new ones to hand when you do the change. Just over 1litre is required so you need two bottles and will have some left over. As to draining when hot thats to let it drain quicker as it will be thin when at temp, if its cold when draining just leave it to drain longer. You may want to use some plastic pipe attached to the oil bottle so you can get it high at the back of the car so it flows into the filler hole till it overflows when it reaches correct level. A;lso9 keep the car level when doing the change seen some cars with over filled diffs, obviously refilled when up on jacks.
https://www.realoem.com/bmw/enUS/showpa ... Id=33_1147
oem site lists the plugs with O ring plus the alloy sealing washer, check the fitment on your 3.0l as diagram is for my 2.5, can't remember if mine had O rings fitted but suspect they only had the alloy washers which I replaced for new.

DMike · Post by **DMike** » Sun Sep 12, 2021 6:27 pm

Thanks guys! For my VIN realoem lists both washers and plugs with O-rings. I guess I’ll then just order both as inexpensive as they are. The aluminium reinforcement plate obviously needs to come off to gain access. Didn’t yet lift it up on the quickjacks but crawling under the bumper the fill plug area seems quite cramped to work.

GuidoK · Post by **GuidoK** » Sun Sep 12, 2021 6:33 pm

Have you already looked if your diff has the drainplug?
And also be sure that you have the right size hex key and that you can reach the fill plug with it.
Applying the required torque with a torque wrench is virtually impossible.

Rockhopper · Post by **Rockhopper** » Sun Sep 12, 2021 6:43 pm

Make sure you can get the fill plug out before you tackle the drain plug.

Zulu4 · Post by **Zulu4** » Sun Sep 12, 2021 6:55 pm

I used a 14mm allen key, cut down a bit with an angle grinder to get it to fit.

DMike · Post by **DMike** » Sun Sep 12, 2021 9:46 pm

Thanks for the tips. There seems to be a hex drain plug. Couldn’t see the fill plug area well bc the car was not on a lift. Ordered today new plugs and washers so I’ll both types available and give it a try in a week or so.

GuidoK · Post by **GuidoK** » Sun Sep 12, 2021 9:54 pm

Zulu4 wrote: ↑Sun Sep 12, 2021 6:55 pm I used a 14mm allen key, cut down a bit with an angle grinder to get it to fit.

Indeed.
I also have a 14mm hex bit, in the bigger size screw bit system (don't know exactly what its called), and with an adapter I could get it on a torque wrench to fit inbetween the diff and frame.
For filling the diff I used a big metal oil syringe with flexible hose

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