Rear diff oil color

[supton]

After spending the weekend trying to find the A/T fill plug on my truck (finally did--too late to bother with that job) I decided to check rear diff fluid. I was planning on changing it, since I have no records it was changed (Carfax or on the CPO work). Oddly enough, it seems clear...? I mean, I stuck a finger in, and most of the oil was clear; then there was blackish fluid around where I touched threads.

Truck had been sitting for like a week (was going to drive it first, to warm it up before changing the oil) but now I'm wondering if it's gotten a change at some point. Seems like most threads I read about virgin rear diff oil going this long usually include descriptions about the oil being black.

 

[Barkleymut]

It is a pretty easy job on the chevy and 2 ford trucks I have changed out. Just change it out and sleep easier. You are right at the mileage that it makes sense to do the job. Just make sure you can open the fill hole before starting.

 

[supton]

Yeah, I was checking on the fill hole, and wanted to make sure I could get that open. I figured, it'd be cheap enough to do; was curious about the initial findings. Maybe what drains out will be pitch black, dunno. Would be stupid easy to do, first vehicle I can crawl under without needing a lift.

 

[NMBurb02]

I wouldn't expect the fluid to get black like motor oil because it is not exposed to the same levels of heat or combustion byproducts. There may be particulates (metal shavings, etc.) in the fluid that you could not see by touching just the top of the fluid because they have had a week to settle to the bottom of the diff. If it is due for a change due to time/mileage, I would go ahead and do it.

 

[NateDN10]

I changed the fluid in both diffs on our Subaru (different beast, I know) for the first time at around 90K miles, and it was relatively clear. There was a light to moderate coating of stuff on the magnetic drain plugs though.

 

[BISCUT]

Change it up and sleep well.

 

[Thermo1223]

When I changed it on the older Forester it was not clear, it was black as heck from oxidizing. I was always told to change it hot so that's what I did. Maybe the dirt settled to the bottom of the diff on the Tundra?

 

[artificialist]

I am used to gear oil going gray, not black. That is because the #1 containment in gear oil is metal from the gears. Sometimes you don't see it from the fill plug, but you do see it on the bottom of the diff if you remove the drain plug or remove the pan. The gray stuff can sink to the bottom.

 

[Thermo1223]

Cheaper dino gear oil perhaps in my case?

 

[artificialist]

Originally Posted By: Thermo1223
Cheaper dino gear oil perhaps in my case?

I'm not sure. I rarely work on Subarus, and I don't see black gear oil anywhere. Perhaps there is something different about a Subaru?