First Diff Fluid Change - Pics

[Joseph_S37]

Hello everyone

I just completed my trucks first differential fluid change at 16,500km. The factory fluid looked mostly clear, but with a gray cloudiness to it. I'm assuming it was some kind of metallic dust floating around. The magnet also had a fair size pile of stuck ferrous dust. I'm assuming both the gray cloudiness and the amount of debris on the magnet are both normal considering the gears were just broken in.

Anyways, here are a few pics, any thoughts would be appreciated.

 

[Oil Changer]

Must be change your differential fluid day. Just finished up my Astro. My gears/fluid look the same. Mine had 75k.

 

[hounddog]

The GREYI I think is from assembly paint.

 

[beast3300]

Excellent job! Thanks for the pics!

 

[Hootbro]

Why so early?

 

[Slick17601]

Originally Posted By: Hootbro
Why so early?


Always a good idea for an early drain on a differential. After break-in, there's very little wear.

 

[Jim Allen]

Originally Posted By: Slick17601
Originally Posted By: Hootbro
Why so early?


Always a good idea for an early drain on a differential. After break-in, there's very little wear.


Yep! A high percentage of the total lifetime of wear metals generated by an axle come in the first few thousand miles (or kms in this case) of operation while the axle breaks in. Since there is no filtration, getting those chunks out is a good thing in the long run.

Obviously, the OEM have calculated how far things can be pushed on the OCI, so if you were to drive the car 100K or so and trade it in, you may never know the difference and that early OC would be a waste for you. Unfortunately, some cars may fall outside those OEM averages and have an early problem that can be traced back to excessive contamination.

They say, "Wear metals beget wear metals," so the more abrasive junk floating around, the more wear there will be. Also, more metallic particles in oil increases the oxidation rate of the oil and depletes the additive package faster as it tries to cope, so with an early change, you have both increased the potential life of the axle, you have increased the working life of the oil as well. If you plan on keeping a vehicle for long periods, or work it hard, it's probably worth the investment.

The pics are worth a thousand words. If that much is visible, think of how much wasn't?

 

[BISCUT]

So true! Very good idea to change out the front differential fluid as well (assuming your Chevy is a 4x4). I waited 30k on wifes Armada...fluid was grey like yours and had plenty of particles on the magnets. If I had it to do over I'd have done it at 10k.

 

[Joseph_S37]

Yes as many have said before me, I changed early to get the initial serge of break in particles out of there. I also wanted to inspect the gears to see if there is any abnormal wear happening. Fortunately everything seems fine.

If anyone is curious, Amsoil SVG 75w-90 went in.


Originally Posted By: BISCUT
So true! Very good idea to change out the front differential fluid as well (assuming your Chevy is a 4x4). I waited 30k on wifes Armada...fluid was grey like yours and had plenty of particles on the magnets. If I had it to do over I'd have done it at 10k.


Yeah I'm planning on doing the front fairly soon here too, but it's a part time 4x4 so besides a few days in winter the front really hasn't seen much work. Not even sure if it's done break in or not... Oh well!

 

[Hootbro]

Originally Posted By: Slick17601
Originally Posted By: Hootbro
Why so early?


Always a good idea for an early drain on a differential. After break-in, there's very little wear.


How is it quantifiable on the back end of longevity to do it early than wait until the first manufacturer's recommended OCI?

Most makes recommend 30K miles or more before doing the first change unless it has been submerged in water.

If people want to change it early, more power to them but I think it is more of a psychological self serving exercise than anything that is truly need before the recommend scheduled change

 

[hounddog]

The fliud is grey with 0 miles. I've seen hundreds over the years on many different manufactures. The grey isn't from wear metals. I was told years ago its the paint used in set up and assembly lube used.

 

[CarbonSteel]

Originally Posted By: Hootbro
How is it quantifiable on the back end of longevity to do it early than wait until the first manufacturer's recommended OCI?

I think this is a good question. In the case of my FX4, Ford states the rear axle lubricant is "good for life". My rebuttal to that is "define life". I changed it at 13.3K and again at 69.6K and the wear metals trended down nicely between the two. The TAN numbers were rising and had it been left for double the OCI (much less "life"), the TAN would have been quite high indeed.

FX4 Axle UOAs

 

[CarbonSteel]

Originally Posted By: hounddog
The fliud is grey with 0 miles. I've seen hundreds over the years on many different manufactures. The grey isn't from wear metals. I was told years ago its the paint used in set up and assembly lube used.

I think this is correct; my Ford OEM was grey, but the next fill (that was OTC) was not. It could be something the OEM adds to the FF for wear-in?

 

[hounddog]

Its set up paint,gear back lash etc. and assembly lube.