Metal flakes in my rear differential fluid

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Looked like tiny brass or bronze (bearing, I guess) flakes to me (golden color). This is the original fluid with 126k miles on it. I replaced it with Redline 75W-90 GL5 gear oil. Will my rear differential suffer sudden and catastrophic failure, or will it die slowly? What's the prognosis, doc?
 
chances are that if you have no whining noise coming from the rear, you'll be alright. When the gears become loose(bearing wear and teeth not lineing up) then you've got problems. You've most likely headed off the problem before it got serious.
 
As far as I can tell, there's no noise coming from the rear differential. I hope you're right about me dodging the bullet...
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quote:

Originally posted by moribundman:
Looked like tiny brass or bronze (bearing, I guess) flakes to me (golden color). This is the original fluid with 126k miles on it. I replaced it with Redline 75W-90 GL5 gear oil. Will my rear differential suffer sudden and catastrophic failure, or will it die slowly? What's the prognosis, doc?

Just thought I'd add that it's normal to get metal flakes when changing diff oil. Many diffs use a magnetic plug to try to catch most of them. Sometimes when you remove a magnetic plug there will be a little pile of metal shavings hanging from it. Nothing to worry about.
 
You should have seen my e-250 after the first 500 miles of breaking in the differential...

There were metal chunks, flakes, "powder", etc...

Same with the Detroit TrueTrac in my Crown Vic.

Those flakes you saw were probably from the original first 5000 miles and they just stuck onto the magnet.

I make it a priority to get rid of the break-in junk after 500-1000 miles.
 
Overheated bits of steel can have a gold or straw color to them, making them look like brass. So too can staining from oxidized lubricant. The best way to determine whether the debris is brass or steel is by using a magnet.

Some bearings use brass cages, but I doubt you'd find that in automotive applications.... too expensive.
 
Good points and thoughts by everyone. Especially the point of scored steel looking yellow, which is something that crossed my mind last night, too!

Now, I talked to a few other people who have the same car, and they said they did not get any flakes when they changed the rear differential fluid.

When I changed the tranny fluid, I used a magnetic probe and found fine powder and small silver flakes that looked like stainless steel. The tranny had been rebuilt by Audi at just under 30k miles, but has had a noisy first gear for the past 66k miles.

I didn't stick a magent in the used rear differential fluid, but I can do that today, since I haven't recycled it yet. Let's see if I can find any yellow metal that's magnetic!

PS: I was told my tranny (don't know about the rear differential) contained a few big magnets, but if that's true, how come not all steel flakes stuck to those magnets?
 
I just dipped a magnetic probe in the old rear differential fluid, and I got a very small amount of steel particles. Those yellow flakes must have been from a bearing. I'll try to find out what materials Audi (or whoever makes the differential) uses.
 
Most differentials and axles use roller and ball bearings with steel races.


Never saw a modern rear differential with ANY brass or bronze parts; Shouldn't be any golden flakes in there. Silver flakes and slivers, sure, not uncommon after breaking-in.


I like to call differential noises "groans." If it isn't groaning or changing sounds at different speeds or upon acccelertaion of deceleration, then it's probably OK.
 
Stainless steel is impossible to distinguish from steel just by looking. I doubt you have stainless steel in your differential. It's just not a metal that's used in differentials.

The transmission has many more aluminum parts and wear surfaces than does the differential. Wear debris from aluminum is probably the non-magnetic part of your transmission fluid contaminants.
 
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I always wonder how many shavings are a result of the crush washer scraping and drain bolt thread abrasion.

Neither the tranny nor the rear differential drain plug has a washer on my car, and there were no shavings on either plug.

quote:

Stainless steel is impossible to distinguish from steel just by looking. I doubt you have stainless steel in your differential. It's just not a metal that's used in differentials.

I said it "looked like" stainless steel (lack of oxidation). I didn't say it was stainless steel. Whatever it was, it was silvery and magnetic.

quote:

The transmission has many more aluminum parts and wear surfaces than does the differential. Wear debris from aluminum is probably the non-magnetic part of your transmission fluid contaminants.

I found magnetic flakes and slivers in the tranny fluid. I didn't see any non-magnetic bits and pieces in there.
 
quote:

Originally posted by moribundman:
Looked like tiny brass or bronze (bearing, I guess) flakes to me (golden color). This is the original fluid with 126k miles on it.

When I drained and refilled the differential oil in my 2000 Ranger this weekend, I saw a similar thing. A small area of shiny gold-colored flakes. It looked like they were floating on top of the oil in a small dime-sized area and there wasn't many of them.

This was also the original oil with 60000 miles on it. No noise or anything, just doing some regular 60K maintenance. Everything else looked pretty normal. Only thing strange was that the magnet was located on the end of the fill plug. There was no other magnet on the inside of the cover or anywhere else. You'd think they would put one in the bottom somewhere.

Weird, huh?
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On Nissans, the magnet is on the fill plug.

I think they try and put the magnet wherever there is less oil turbulence so the turbulence doesn't wash the particles off the magnet.

In my '92 Burb, the magnet is located on the diffy cover to the right of the ring gear about 1/3 of the way up.

[ October 06, 2003, 04:15 PM: Message edited by: MolaKule ]
 
quote:

Originally posted by MolaKule:
Most differentials and axles use roller and ball bearings with steel races.


Never saw a modern rear differential with ANY brass or bronze parts; Shouldn't be any golden flakes in there. Silver flakes and slivers, sure, not uncommon after breaking-in.


I like to call differential noises "groans." If it isn't groaning or changing sounds at different speeds or upon acccelertaion of deceleration, then it's probably OK.


MolaKule, groaning would be a good way to describe the sounds my diffy is making. Mostly from a stop or low speed manuevering (maybe that is the only time it's noticeable).
I was under the car recently spining the rear wheels by hand and there is occasionally a grinding sound near the front of the diff, so I was thinking my input bearing was going bad.
1989 BMW 325is by the way, 182k miles.
What do you think?
Can you tell if a bearing is going bad/dragging or whatever it's doing through a simple UOA?
After a long drive all areas of the diff are the same temp. And I I can hold my hand there fairly long, so I'd estimate it no hotter than 150F. So then I was thinking it might not be the input bearing? (Wouldn't it create more heat in that area?)
 
Normally a rear end gives fair warning: It will moan, whine, howl etc varying w/ speed. It will typically only do this under lead like cruising or accelerating. If you coast or let off on the accelerator it should quiet down again.

I milked one old car for years like this by keeping the stereo turned up extra loud.
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There is no magic pill lubricant or additive AFAIK - the ring gear set will have to be replaced ultimately. But I had some luck in masking the noise w/ a bandaid of heavier 85W140 FWIW.

If one's ears are sensitive to this type of noise and pick up on it very early - I wonder if there is a particular grade or type of oil that might help hold the wear and noise where it's at - I dunno - just asking.
 
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