I just got finished changing my front/rear diff fluid for the first time, my dealer claims its not necessary and didn't do it on the 'free' first service. The dealer also put in 10w-30 kaw oil in the engine. So much for service. I've since installed amsoil synthetic 0w-40 in the engine and front diff, and kawchem in the rear.

When I drained the rear, it was pretty grey/milky in color, as was the front, but the front much less so.

Anyone else have this? Is this from riding in water?

 

The breathers for the front and rear diff are behind the speedometer. You probably didn't get water in them.

I think that color comes from the brake material on the rear fluid, and/or the use of the brake causes the oil to be this color.

The front diff gets brass looking flecks in it from the diff locking clutch. The 0w40 synth oil is a bit too thin for the front diff in my oppinion. It reduces the unlocked diff stiffness. I use 20w50 synth and it is still a little thin. 20w50 conventional oil is a bit stiff, especially in the cold. I found out the hard way with stiff steering. Next time I change it I will put thicker synthetic in it.

I just change those things often and don't worry.

 

That color is caused by water or moisture in the gearbox. Don't worry though the smallest amount of moisture can change the color of a lot of oil. The brake dust will actually make oil look either dark (depending on abuse) or the small flecks can add a shine to the used oil (metallic).

 

My rear oil was gray too, but the front looked fine.

Andy

 

Just a thought....
Be careful when removing and installing the fill hole plugs. The O-rings can be rolled and broken once in awhile. I had this happen, and luckily I caught it before I went riding.