Differential Fill Level - To spec or to fill hole?

smiller

2008 View J (2007 NCV3 3500)
I just changed the axle lube in my 2007 NC3V 3500 and filled with the specified 1.8 liters (Mobil Delvac 75W-90, MB 235.8). This leaves the lube level 1/4 - 1/2" below the fill hole. I searched and found some limited discussion of this in various threads but the responses usually amount to 'I do this' or 'I do that' but there has to be a correct answer. I'm hesitant to fill beyond the specified amount and bringing the level to the fill hole would significantly exceed that. What is correct?
 

Aqua Puttana

Poly - Thread Finder
... but there has to be a correct answer.
Running it with a true factory fill must be ok. I guess the "correct" answer is the OEM amount, but are you certain that the amounts you added are truly accurate? How was it measured? Did they properly fill the containers you purchased?

... I'm hesitant to fill beyond the specified amount and bringing the level to the fill hole would significantly exceed that. What is correct?
I'm not so certain that it is that critical. It's a basic sump in a differential. I prefer to have all the fluid that can safely be maintained on the basis that more fluid is better for cooling and leaves a bit more margin in the event of an unknown loss of fluid.

My 'I do this' or 'I do that:

Being that you are concerned about overfill I would take the truck out on a hot day and get the differential up to temperature. I would then remove the plug and top off.

That said, I'd be interested to hear the history of problems encountered by the thousands of Sprinters who are running with the differential fluid filled to the bottom of the plug whether hot or cold.

:cheers: vic
 

CJPJ

2008 3500 170"ext. 3.0 V6 OM642.993
The fill hole stipulates the correct oil level, ... provided that the vehicle is (level front to back & side to side).

:2cents:
 

smiller

2008 View J (2007 NCV3 3500)
but are you certain that the amounts you added are truly accurate? How was it measured? Did they properly fill the containers you purchased?
Two 1-quart (950 ml) containers, so I guess it's actually filled to 1.9 liters. OMG... overfilled!! :laughing:

The fill hole stipulates the correct oil level, ... provided that the vehicle is (level front to back & side to side)
OK, but that begs the question as to why the factory fill spec is so far off of that amount (by at least a pint.) And the factory service manual says 'REAR AXLE ± 0.03 Liter (1 oz.)' Why specify such a tight spec if it doesn't matter?


I'm sure it isn't going to blow up either way, just mechanically curious.

.
 
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Dingo

New member
One reason for an exact quantity fill is that it is easy to put a cost value on each axle filled at the factory . The bean counters are only interested in bottom line costs & every axle filled to the bottom of the filler plug could require an extra 30c worth of oil , this cost over 1000 axles means a boss cannot afford his coffee that morning . I asked exactly the same question when on a factory tour of a well known UK based manufacturuer & that was the answer i was given Given quantity = known cost per unit , extra means loss of profit . Personally , i would fill till oil dribbles out the fill hole .
 

Aqua Puttana

Poly - Thread Finder
One reason for an exact quantity fill is that it is easy to put a cost value on each axle filled at the factory . The bean counters are only interested in bottom line costs & every axle filled to the bottom of the filler plug could require an extra 30c worth of oil , this cost over 1000 axles means a boss cannot afford his coffee that morning . I asked exactly the same question when on a factory tour of a well known UK based manufacturuer & that was the answer i was given Given quantity = known cost per unit , extra means loss of profit . Personally , i would fill till oil dribbles out the fill hole .
I like the logic. :thumbup:

When in doubt... Follow the money.

:cheers: vic
 

BBlessing

61k happy miles
it may be that since the filler plug is a rubber plug, you want the fill level just shy of the fill hole to prevent leakage.

bb
 

smiller

2008 View J (2007 NCV3 3500)
it may be that since the filler plug is a rubber plug, you want the fill level just shy of the fill hole to prevent leakage.
Yes, that could well be one reason. Two other reasons for a specific fill amount I have come across while researching the topic is 1) too high a level can cause foaming and discharge through the breather vent (or create excessive internal pressure if the unit is not vented), and 2) the relationship of the oil level to fill hole depends on the alignment of the differential in a specific vehicle (which can vary in order to support a proper pinion angle), while a specific fill volume is not dependent on this and is thus more accurate. Whether any or all of these came into play when MB specified the fill amount I cannot say.

.
 
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CJPJ

2008 3500 170"ext. 3.0 V6 OM642.993
Sunday am. before the start of Supper Bowl 50
Remove and replaced the NVC3 3500 differential oil @ 60,350mi.
First I took the van on a 1hr highway loop to warm the oil; the diff. felt warm to the touch. l wanted to capture the first oil out; was slightly surprise at the velocity it came out, .. probably over filled the small bottle times 2.5 or 3 . Captured 9.5oz of dark brown used gear oil.
Let it drain about 1hr.
Crawled under the extended; getting ready to fill but I can't locate the drain plug, not on the 14mm Allan; :thinking: about 20 minutes of soul searching, asked the dogs, contemplated buying another, thoughtfully remembered unscrewing the plug: ... It's in the small sample bottle!
The fill hole stipulates the correct oil level, ... provided that the vehicle is (level front to back & side to side).:2cents:
Crawled back under, proceeded to fill the diff with Mobil Delvac Synthetic Gear Oil from a 1U.S.Gal/3.78L container.

It took 2.28L or 2.41 quarts to fill.

Then after a 10mi. + round trip drive to dispose of the used oil, l crawled back under and pulled the fill plug and got what I wanted ; a slight clean weep from the fill hole.

:thumbup:

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smiller

2008 View J (2007 NCV3 3500)
Yeah, I went with the groupthink and ended up filling to the fill hole too, took about 2.5 quarts. This is contrary to the service manual which states 1.9 quarts +/- 1 ounce, but what does the service manual know anyway? :smilewink:

FWIW after about 5k miles I haven't seen any leaks or overflow so the boring answer is probably that it just doesn't matter much either way.
 

NOMRAD

New member
i just drained and measured the amount of diff oil that cam out of my 2008 dodge sprinter 3500.
i believe it was still factory oil. 2.2l came out .
i called the mb dealer and asked him how much to put in . the parts guy said 1.2l so i said please check with service who said 1.8l.
i ended up putting 2 l of mb oil in and it is 1/2 below the rubber plug .
 

Aqua Puttana

Poly - Thread Finder
i just drained and measured the amount of diff oil that cam out of my 2008 dodge sprinter 3500.
i believe it was still factory oil. 2.2l came out .
i called the mb dealer and asked him how much to put in . the parts guy said 1.2l so i said please check with service who said 1.8l.
i ended up putting 2 l of mb oil in and it is 1/2 below the rubber plug .
The method with the old Dodge B250 differentials was to fill until the level was touched with your fingertip insert and bent down in the fill hole. That was about 3/8" - 1/2" below for most finger dips. I believe that the idea was that when the differential heated up the heated oil and assembly moved the level up to just below the fill hole.

Many times the Dodge differentials got filled to the fill hole. It didn't cause any problems which I'm aware of.

Almost to the fill hole should be fine. It is a sump. A bit less volume of oil isn't that critical. Maybe the level not being above the rubber plug when hot is a good thing. :idunno:

The numbers I've seen for 2500 differentials is 1.6 to 1.8 quarts for refill.

I'd be more concerned that the level was correctly up to or near the fill hole than I would be about what volume it is *supposed* to take.

vic
 

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