WRX gear oil

[tom]

I just replaced my MT and rear diff oil on my 02 wrx wagon. It's got
30k on it and I put in Amsoil Series 2k gear oil. The MT oil came out
looking brand new. There were some metal shavings on the magnetic
drain plug, but the oil itself was clear. The rear diff oil was
another story. It came out gray/black! Any comments? I drive it 60%
highway. No racing or rally. I don't understand why it looked so bad
at 30K. Thanks.

 

[null_pointer]

One possibility is that some molybdenum disulfide (MOLY) was added to
the oil. Similar in appearance and action to graphite, it is
sometimes used where two hard pieces of metal (such as a ring and
pinion geat set) slide across each other. It supplies extra extreme
pressure lubrication. I don't think it is used in transmissions due
to it's ability to keep the synchro rings from "gripping" the cones
properly.

 

[Edward Hayes]

Subaru Differential oil is gray and probable do to moly additive. It is good
stuff as it has no change interval for cars driven normally. eddie

 

[David & Caroline]

I found the same thing in my rear diff (also an 02 WRX wagon, actually) - I
also noted what was almost like a grey gel on the bottom of the differential
case (this was at 6k miles, too - I was just doing my normal "swap
everything over to synthetic" treatment, rather than waiting for the gear
oil to get bad...) - I was curious if some of the threadlocker which Subaru
uses got in there (they appear to be pretty generous with it, and it is
black in color...) - be curious to see how you like the Amsoil 2k in the
transmission - I have heard people gripe that it is a little to slick for
proper synchro function (no experience with it myself) - I went with Motul
Gear 300 in the trans and rear diff.

As an aside, in very aggressive driving, you can overheat the rear diff, and
cook the fluid a bit (which is why the STi has a temp. sensor in the rear
differential) - obviously didn't happen here, but just something to watch
out for.

 

[tom]

The shifting is markedly smoother now. I haven't really driven it
aggressively since, so I don't know about the synchros not meshing
quickly or what not. My tires are worn out and I'm waiting to get
snows on. I did look into getting redline initially because of those
comments (saw them on Cobb Tuning), but I couldn't find a local
dealer. And since I do 80 miles a day in commute anyways, the Amsoil
is probably a better choice for me. I hear you about the threadlocker.
There was quite a good chunk of it on the bolts.