My biggest concern is that it came out at the top. Generally, that stuff sits down at the bottom. It's normal to have a little in there, but with it being up top - you need to inspect it.

This is mine after about 15,000 miles. It still looked new. I was replacing the pinion seal here.

 

LOL.... yeah, one of these days I need to up my game on the welder. My Dad keeps telling me he's going to give me his Lincoln, which will use argon.... so I've kinda held out. It is a single or two phase unit too.... kind of a cool welder.

I finally got to lay down some white on the door jambs.... I'm digging it.

 

VERY unusual. You hadn't mentioned seals, so it's breathing I take it. I'd have to guess, completely incorrect gear oil was used, - or contamination....perhaps from a missing breather hose....Has to be something along the lines. Doesn't matter what you tow or how hard.

 

> Gasket surface of rear diff cover should be super clean.
That's the main concern.

Uh, ok. A lil premature, to me.
NEVER seen a silverized oil.
Din't think I had read of one w graphite.
Maybe.. molybdomen?
Guys? Silverized gear oil?

You gotta do it your way.
I and "my team," (when applicable,) always seem to be behind all others. Prep, prep, prep.
Then we calmly, won the non-race, and, with a better quality of work. 30 minutes, a lil tight for me. 2 hours? Maybe I'd take it slow. Examine my trailer connector while things drain. Watch the oil drip, drip through the filter. I'm retired. An hour can be adequate. Can be. YMMV. I take things, slower. Call it Virgoistic. Californian. Retired. PTSD. You, go be you. Until that doesn't work. As a non-pro, it's good to take things slowly. It helps avoid, mistakes. Oversights. IMHO.

 

Silver oil, I've seen it many a time. Usually, the upper pinion bearing goes out, stressing the load on the R&P, causing extreme pressure wear and metal into the oil.

Also a milky grey from water getting into the differential. Either the vehicle got in water over the axle or the vent tube came loose and sucked water in as Brew mentioned..

There was a lube with moly in it available, but these rear ends take a synthetic gear oil, so that is highly doubtful it was used and has become difficult to find, at least in my area.

 

Doesn't make sense to me.

I guess there could be a serious amount of sludge hiding somewhere that's being missed. I've flushed them with cleaner if noticed. Silver is a contamination color...so is brown along with watery black. They can take some abuse...

Confirm breather integrity as well.

EDIT: Hadn't seen AK's post before this one...his is more thorough.

 

GRF - I believe my gut is probably backed up my those with actual experience. Maybe plan more than an hour, just in case.

I can advise how I turned a long handled SS BBQ into a bore-brush. The axle tube welds are crude and unfinished inside, and catch metal paste that you must delete. I wonder if a regular pressure washer could help. I could not try it, where I was.

Anyway, adding a qt too much for a few days didn't do this.

 

Can someone throw me a few clues with the breather hole on the rear diff ?
What should I look for ?

sounds to me that it's not working or water got into that breather hole some how.
I never went thru deep water.

I saw silver metallic color on previous oil change. That one was Motorcraft 75 W 140, this one here was also 75 W 140...
Motorcraft friction modifier was added too !
I was in front when the tech changed it....

 

 

Water is wishful thinking. Water + oil makes "peanut butter". I'm afraid you have a rear end that's eating itself to make the oil silver.