Sealed for life diff

Nick177

Nick177

Member
The z passed it's mot last week,and while it was in the garage I asked them to replace the diff,gearbox and engine oil.the engine oil has only done 4k since it was last replaced, but vanos always benefits from an oil change.
Above 30 mph the car has a slight whine coming from the diff or gearbox, so I asked the mechanic to replace the oils in both.
He stated that the diff was sealed for life,so I asked him to replace the oil anyway. The diff only has one drain plug which was clearly for topping up only. The garage had to buy a suction pump,and replaced both oils.
After the mot, I took the car for a spin,and result ! The whine has completely disappeared.
The car is a 2006 2.5 and has done 49k, and replacing the diff and gearbox oil has resulted in smoother gear changes and a silent diff.
The car has a full service history, and it has clearly benefitted from this extra service,which is good because I had this extra work done in preparation for touring Germany in a couple of weeks time. :)
 
Afaik the z4 diff has 2 plugs.
The fill plug is located in the rear lid (and for that you'll probably an oil siringe with flexible hose to fill due to the angle), and the drain plug is located at the side.

Like this:
31.jpg
(drainplug clearly visible)

Draining....
6.jpg

The oil is 'sealed for life' (according to bmw), but refreshing the oil never hurts (as long as you use the right oil)
Refreshing oil is also a certain way to make sure that the oil level is correct. That is really important.
 
Hmm yes strange.
I've looked in TIS and there are 2 procedures for refreshing the oil, and indeed one is for if there's only 1 plug.
So bmw uses multiple diff casings.
 
srhutch said:
Guessing the OP has a N52 2.5, so could be they changed the diff casing on face lift models.
Click to expand...

I've got a 2006 3.0si sport and the diff had 2 plugs when I changed the diff oil.
 
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