Milky Gearbox Fluid - What does it mean?

[kmoush]

I recently purchased my '86 911 Coupe (my first 911). As part of the initial PM efforts, I replaced the gearbox oil and when I drained it noticed the color was a gray milky color. This seemed odd, since every manual transmission (Audi) I have replaced the fluid on, the draining fluid is dark brown. I thought perhaps the color may have been inherent in that of the previous fluid. As such I replenished the fluid and drove the car perhaps 1000 miles before, flushing and replacing with new. The photo attached shows the color of the draining fluid (same in both instances). In both instances I replaced the fluid with Castrol 80/90, per Bentley. Is this color a sign that detrimental wear (aka imminent gearbox rebuild) is occurring or is this coloring something that can be expected?

Note the drain plug magnet did have very fine metal deposits attached, no alarming amount, but no metal chunks.

[Eric Hahl]

Sounds like moisture.

[85911]

^ Whenever I have gotten water in any oil, it turns to a chocolate milkshake color.

[yelcab1]

Where would the water come from?

[kmoush]

The car now resides in San Diego, and has not been driven in any rains....definitely not in the current El Nino.

[KNS]

I hope this isn't the case but if the car was in a flood/high water it could get in through the upper breather.

[kmoush]

For that to happen I would assume the car would have exhibited some signs of water damage in the interior. I did not see anything like that when I pulled the interior and detailed the interior and all the carpets. But I could be wrong.

Assuming it did not encounter such hi water, I am still baffled by the color, and if air moisture were the culprit it seems odd it would have this drastic affect.

[Scott Douglas]

Where did the car come from?
Sounds like it could be condensation build up from a lot of short trips where the gear box never reached a high enough temp to boil off the condensates that form inside.
Do you know how long the fluid had been in there?

[kmoush]

Photo of draining fluid.

[kmoush]

The original owner, Menlo Park CA, second owner LA (owned car for 13 months) now myself in San Diego.

I do not know how long the fluid was in the car originally. Between the changes I did, 5 months and about 1000 miles.

[Quicksilver]

The moisture came from the air. The case is vented to the atmosphere. The case cools during the evening and during cooler weather condensation will form inside the case. Once that condensed water gets into the oil it will tend to go towards the bottom where it can't evaporate again.
The process repeats everyday as new air is pulled in when the temperature drops in the evening. Any vented lubrication system will gather moisture unless it is heated regularly to boil it off.
Once the water is in the oil the churning action of the moving parts will emulsify the water and oil and it will appear milky.

What you have is a car that probably wasn't stored in a heated garage and it wasn't driven regularly to heat the gear oil to the point where the water would boil off. If it came from a cold climate that will greatly increase the chances of this happening.

[kmoush]

Yes, I would tend to agree water in the fluid can lead to that color as a result of emulsification.

I have to assume this is something that is a non issue. Having worked in Stuttgart for 3 years and experienced the crazy amount of cold, rain and moisture in So. Germany, and the fact that the majority of Germans don't have garages, and would never think of having a heated one, this issue would be expected and engineered into the design.

Now that the car is in SoCal the affects of this should be not as prolific.

Thoughts?

[DRACO A5OG]

OP, did you warm up the car before draining or cold?

I personally like to drive her around prior to gear box lube dump.

[kmoush]

Yes, the second time I had to drive 45 minutes (all freeway) to the lift where I did the draining (car on lift in photo).

[ClickClickBoom]

Two possibly three ways for moisture to get into the gearbox.
1) Atmospheric
2) Driving under water, or splashing and bad seals, or combo of any or all.
3) Car/motor washing technique.

Highly unlikely other possibility, would be mechanical damage to the trans case.

[DRACO A5OG]

Very Strange indeed.

I wonder what your next change will look like???

[Quicksilver]

Originally Posted by kmoush

Yes, I would tend to agree water in the fluid can lead to that color as a result of emulsification.

I have to assume this is something that is a non issue. Having worked in Stuttgart for 3 years and experienced the crazy amount of cold, rain and moisture in So. Germany, and the fact that the majority of Germans don't have garages, and would never think of having a heated one, this issue would be expected and engineered into the design.

Now that the car is in SoCal the affects of this should be not as prolific.

Thoughts?

You posted the pic while I was typing and what you have is jaw dropping. I would have to agree. I was expecting some milky streaks leading to a much darker color. It takes a lot of abuse to get that level of water in it. We used to see serious moisture (but still not to your level) during long cold snaps in Alaska. They would see repeated heating to around room temperature followed by freezing. In the engines you would even see what looks like brown/grey pudding collecting inside the valve cover from the quantity of water building up.

I would guess that water was directly introduced. I wonder if the vent was exposed to a power washer or something. It is good that you got it out of there because you don't want the transmission corroding on the inside. I would have the vent checked. If there was a "normal" leak in the upper trans such as a pad gasket or seal, I would expect there to be a very obvious leak of trans fluid.
The only other source I can think of besides the vent is if it was actually put into the trans. Either sabotage or maybe someone cheaped out and drained the fluid into a container that had some water and the refilled the the trans from that container. Seems like a longshot but what you have is breaking the "Odd-O-Meter" already.

One thing you will want to do is go on an extended hard drive to seriously heat that trans and "boil" it out. (A great excuse for a track day!)

[Lyle O]

Get a little pump and pull some oil out now (from the fill port) and see what it looks like. Assuming it is relatively fresh, you can check it like this every so often to see at what rate it changes. It should, at this point, be showing few signs of water emulsification. As DRACO says, be sure to warm it up before you sample it (but be careful not to burn yourself). Also, be sure you didn't put in limited slip oil unless you have a LSD (Castrol makes 80/90 for LSD). If it already is milky, something strange is going on...Good luck.
Lyle.

[Matt Monson]

You have a blown head gasket...

Sorry. I've got nothing. This is a weird one. Once could be explained. Number two time just doesn't make sense.

What was in it before? Redline Shockproof? All the calcium in that junk comes out of suspension and leaves crud all over inside the gearbox. That's the only thing I could think of that would make it happen twice.

[kmoush]

Originally Posted by Matt Monson

You have a blown head gasket...

Sorry. I've got nothing. This is a weird one. Once could be explained. Number two time just doesn't make sense.

What was in it before? Redline Shockproof? All the calcium in that junk comes out of suspension and leaves crud all over inside the gearbox. That's the only thing I could think of that would make it happen twice.

Cannot be the head gasket.....I fixed that with some JB weld. Miracles!!!

I do not know what was in the gearbox when I bought the car, however both times I put in Castrol 80/90W, and not "limited slip", followed the API specs mentioned in the Bentley.

Yeah this one has me stumped.