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Discussion Starter #1
I dropped my FD oil today and the oil was black. Drain plug was free of metal particles and sludge. The wheel does not have any movement.
Could this be a early sign of FD failure?
Crown bearing rubbing the seal turning the oil black ?
The oil was the red BMW synthetic. I have used this oil before and never had this discoloring occur.
Decided to refill with red synthetic and rode 50 miles. Drained the oil again and it started to darken.
BMW dealer mechanic said he has noticed the FD oil turing black with the red Syn.

Anyone els experence this?
 

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My BMW 75W140 Synthetec gear oil color was almost original looking after 8k miles in the FD. Same out of the tranny.
 

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Discussion Starter #3
Silverhair said:
My BMW 75W140 Synthetec gear oil color was almost original looking after 8k miles in the FD. Same out of the tranny.
This has been the case in the past, even after 11000 mile interval changes.
 

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I don't believe that oil color is any indication of FD failure.
Metal particles above a certain size, yes, but you report none.

I have heard that water contamination of some oils will cause color change.

I'd just change the oil and don't worry. You don't have any symptoms of FD failure that I know of.
 

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I'd send a sample in and have it analysed. Would answer many of your questions, including water contamination (emulsification).
 

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As cheap as gear oil is, why not try a different brand of oil for a hundred miles to see what color you get,
I use Mobil I synthetic and it always comes out looking just like it went in.
 

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I also use Mobil1 syn. & it always comes out a very dark green almost black. Its so easy to change I usually change at near 2,500 miles. I drain it into a clear mason jar & after a week I look at bottom & so far so good.
 

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Discussion Starter #8
CharlieVT said:
I don't believe that oil color is any indication of FD failure.
Metal particles above a certain size, yes, but you report none.

I have heard that water contamination of some oils will cause color change.

I'd just change the oil and don't worry. You don't have any symptoms of FD failure that I know of.
Charlie thanks , your feedback is reassuring.
Perhaps the mason Dixon rally next weekend has me over thinking this. True water in oil tends to turn the oil white.

Thanks,
Fingers Crossed !
 

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Discussion Starter #9
fpmlt said:
I'd send a sample in and have it analysed. Would answer many of your questions, including water contamination (emulsification).
Thanks , I may try that.
 

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Discussion Starter #10
SilverBuffalo said:
As cheap as gear oil is, why not try a different brand of oil for a hundred miles to see what color you get,
I use Mobil I synthetic and it always comes out looking just like it went in.
Thanks Hans !
Watch what you say, I was using that over priced BMW oil $14 per quart.
What grade of M-1 do you use in the FD' / Trans motor ?
 

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Discussion Starter #11
saddle-man said:
I also use Mobil1 syn. & it always comes out a very dark green almost black. Its so easy to change I usually change at near 2,500 miles. I drain it into a clear mason jar & after a week I look at bottom & so far so good.
Thanks Dave, I ran red bmw oil then bmw hypoid both turned dark in color only after 50 miles..
 

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I also should have said that the different gear lubes I have tried Valvoline & Mobil1 have always come out a very dark green. It didn't seem to matter how many miles either. From a few hundred miles to over 8,000 miles.
 

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Odd on colors people are experiencing.

Trany and FD every 3000 and in both it is the golden color as when it went in.

I would try a golden color as suggested and then check it. Seems this will give you a very quick and easy way to check it before you are off on your trip.

It is very odd I think that after you have experience with this product for it to all the sudden change?

Hope you find out it is just the fluid type has changed somehow.

Important thing is you are finding no "chunks".
 

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Housing material is ALUMINUM, and when you rub aluminum the color is BLACK .... So my guess would be the Large crown bearing is no longer a light press fit into the carrier hub and now is spinning wearing away on the housing ? ... thus producing the blackened oil.

Guess :rolleyes: ... it all it is.
 

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Water in regular gear oil turns it cream color. Water in synthetics turns them black. I don't know why but it just does. Be careful if you are using a pressure wand around the final drive unit as you may be injecting a small amount of water into the unit when you are washing the cycle. You may want to check your gaskets on the filler plug and ABS sensor as well to make sure they are fully intact.
 

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When I replaced my final drive the mechanic at the BMW dealer used a magnet to show me the shavings. This would be a better indicator of the status of your final drive.

Hope this helps.
 

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Discussion Starter #17
BeemerBoyLT said:
When I replaced my final drive the mechanic at the BMW dealer used a magnet to show me the shavings. This would be a better indicator of the status of your final drive.

Hope this helps.
Agree , Plus the magnet on the drain plug.
 

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Discussion Starter #18
deanwoolsey said:
. Water in synthetics turns them black. QUOTE]

I will test that tonight , have to pour some water in a sampel of syn oil.
 

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That's from my experience with the bottom end on my outboard motor. It should be the same on the FD unit but probably only shows up with some wear.
 

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You can also put the magnetic drain plug into a glass of mineral spirits paint thinner and stir it. The iron particles stay stuck to the magnet and are then visible while any aluminum flakes will tend to settle rapidly to the bottom of the glass and can be readily seen with a strong light source before the lighter gear oil has time to settle out.
 
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