Factory fills of rearends. When to change? Photos.

[Bill in Utah]

Hi,

First of all, I know without a UOA we really don't know the condition of oil.

But, How a fluid is operating (making noise, hard to shift) would either indicate a poor use of the fluid (wrong type) or worn out fluid IMO.

Here are 2 photos. First one is from the rear end of my 2007 Outback. Miles 500. No problem with operation, just flushing out the metals with a cheap fluid before putting in some better oil.



And the 2nd photo here is the fluid out of a 2002 Chev Silverado 1500 front axle. No problems except we wanted to get it changed out @ 5 years old and 40k miles. Factory fill.



I find it interesting that both showed some serious metal "glitter" when viewed in the sun.

One with 500 miles and one with 40k.

All I can say is the fluid coming out looks nothing like what is going in.

Again, looks are not everything...

Take care, bill

 

[Winston]

It is amazing how quickly differential fluids turn black. Where does the black color come from? Heat?

 

[PT1]

I have a friend who is a test engineer at a major tier one differential/axle supplier and recommends changing diff/axle lubricant at 1000-3000 miles because all of the initial break-in wear has taken place by then and the lubricant usually contains lots of debris. If there is no magnet to catch the debris then he said 1000 miles for certain. But that look is not uncommon. All my truck diffs drain out like that with the initial drain.

 

[PT1]

Quote:

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It is amazing how quickly differential fluids turn black. Where does the black color come from? Heat?

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As I understand it heat plus wear in metals from the gearsets and bearings and other powdered metal bushings, assembly fluids, casting dust,secondary machining dust,all that good stuff you want rolling around in there for 50,000 miles...

 

[Panzerman]

I changed the rearend oil in my 2006 Dodge ram at 3000 miles, it is factory fill Mobil 1 75w90 and it was NASTY. It was grey and metally. Iam going to change the front rear at 8000 miles, now that I found out it is full time 4wd, and the front axle doesnt kick out. A finger check revealed it not to be as nasty though.

 

[JTK]

The synthetic 75w-90 was black in my 2005 trailblazer @ 22Kmi and about 1.5yrs in service. It's an AAM rear. The front diff oil looked the same.

 

[H2GURU]

Bill,
I have a little Toyota truck and the owners manual says to change rear axle fluid at 30,000 miles, probably due to the fact that I have an electric locking axle. I used Mobil-1 75W-90 and it comes out just as clean as I put it in. Going to a SYN will probably not even cost you any more as you will realize a very slight milage increase and this will off-set the higher cost. All big fleets have used SYNTHETICS in the final drives for years with excellent results . You should have a MAGNET on that drain plug that will retain all that "glitter". GOOD LUCK.

 

[Sparkman]

I've found that once the axle is well worn in, say 75k or more, the synthetic lubes will stay light colored for a very long time.

I'll agree that changing out the factory fill relatively early sounds like a good idea.

 

[Steve S]

Quote:

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I have a friend who is a test engineer at a major tier one differential/axle supplier and recommends changing diff/axle lubricant at 1000-3000 miles because all of the initial break-in wear has taken place by then and the lubricant usually contains lots of debris. If there is no magnet to catch the debris then he said 1000 miles for certain. But that look is not uncommon. All my truck diffs drain out like that with the initial drain.

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That is the best thing you can do.