D4 - diff and transfer box fill holes - level with full capacity or measure the fluid

[twr7cx]

While looking for the drain and fill plug torque settings I noticed that there's mention in a few of the guides that when refilling the front and rear diff (axel oil) and transfer case oil to measure out the specified capacity and only fill that in, rather than just filling until the oil level reaches the bottom of the fill hole. Are the fill holes therefore not in the correct position relative to the full capacity (i.e. are the fill holes above the level where the oil reaches when filled up to specified capacity)? Seems like an unnecessary complication...

[101RRS]

That is correct - you are supposed to measure the correct amount of oil for the diffs and tfr case and put that in.

However the amount is close to being the same as filling to the bottom of the fill hole and that is what I now do and have had no issues - there is probably less than and extra 50ml (guessimate) that goes in.

[DieselLSE]

Just to clarify, the diffs must be filled by volume only. And it is a different volume for each diff and different volume and oil for the (rear) e-diff.
The transfer case, however, can be filled to the "fill" plug as it is positioned at the correct volume.
Not sure why this is not the case for the diffs.

[twr7cx]

However the amount is close to being the same as filling to the bottom of the fill hole and that is what I now do and have had no issues - there is probably less than and extra 50ml (guessimate) that goes in.

At that close it seems the lazy way is probably close enough...

Not sure why this is not the case for the diffs.

Seems silly not to. Just an added complexity for no extra benefit.


I wonder how many mL of old fluid/oil remains inside after a drain...

[scarry]

My Indie has done thousands over the years,and fills them to the level plug,no issues.

[Geedublya]

My Indie has done thousands over the years,and fills them to the level plug,no issues.

My L494 has basically the same diffs and to my surprise the manual says fill until weeping from fill hole.

Volumes were the same as my old D4.

[Eric SDV6SE]

I changed all fluids at Christmas, including front and rear diffs, transfer case,engine oil and coolant.

i measured the required volumes out for each one after a “drain and wait” (I.e have a coffee while waiting for it to finish dribbling). Would you believe the measured volume that goes in fills to the fill plug and you get a little dribble out...

so next time, I’ll just fill to the plug and do it the old fashioned way.

[PhilipA]

Maybe they are afraid that you will fill it on a 40degree slope.

Regards Philip A