Change Driveline Fluids Early!

[CarbonSteel]

If you always get metal paste, I would say your not changing your fluid often enough. Many do no change gear dope the entire life of an axle, not saying any time interval would not work.

Admittedly if I was paying to have maintenance work done I would not change so often, or if I did not have a convenient place to do the work. I get enjoyment from maintenance activities, almost as much as actual machine use. The way I look at it I invest all my cost 'savings' into better materials. I keep my machines long term, if one has no plans to keep a car just do the bare minium recommended (this is why I never buy used).

I disagree to a large extent, but it can depend on load, operating conditions, oil type, and viscosity. You have two gears moving at 90° to each other under incredible shearing forces that will cause wear metals to be generated. Sadly, Dana 44 Advantek axles produce more for long periods of time versus other axle types. Ergo, you will always see paste on the magnets if the run is at least a few thousand miles.

In my 2019 Wrangler that has the same axle as the Bronco, I regeared from 4.10 to 4.88 to 5.13. On both sets, I had them REM Isotropic polished which produces a near chrome like surface finish and completely eliminates the need for heat cycles during break-in. It also substantially reduces the wear metals generated—but there was still wear metal collected on the magnets. It is just something that cannot be avoided, but can be reduced by the polishing.

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[Callelk]

You can follow my UOAs here

Interesting, do find your T-Case numbers to be typical at 9.5K?

 

[Ziemann]

'23 Big Bend 2-door 2.3L Manual Transmission - spends annually 3+ months in 4WD and tows 3,000-5000 miles/year. Fluid Change Complete.

This is my second fluid change on the MT88 (done again because I have "the noise")- but the first on the diffs and transfer case. My first change on the MT88 was at 1800 miles at break in, and this one was completed at 24,000 miles.

Front Diff: Existing fluid was much darker than expected with minimal metal sheen in the oil pan. Expected goo on the drain plug magnet. Replacement Fluid: Amsoil Severe Gear 75W/90. The Amsoil was on sale and available at my local NAPA. Win.

Rear Diff: As expected- normal goo on the drain plug and dark colored fluid w/ a metal sheen in the oil pan. It needed to be changed. I wiped out the diff with clean cloths and was surprised to see how much goo was settled in the bottom of the diff. Replacement Fluid: Amsoil Severe Gear 75W/90. @CarbonSteel recommends a higher viscosity (which is good advice) based on the belief that the higher viscosity will handle heat better and resist breakdown. I don't have a problem with that logic. Amsoil is a very well proven synthetic, and should also handle the heat very well and resist breaking down even at 75W/90 (which is now Ford's current recommendation). I don't see a problem either way. As @CarbonSteel has stated, the most important factor is how frequent you change the fluid, and not the viscosity in that rear diff.

Transmission: I have had the grinding noise in my MT88 manual since around 800 miles on the vehicle. My MT88 has always performed well and shifts like a dream in spite of "the noise". At 1800 miles at break in, I changed the OEM fluid out for BG Synchro Shift II. That was a great fluid, and it performed very well even during the winter. The fluid was in great shape and probably didn't need to be changed. This change, I used Redline MTLV. I found it IN STOCK at a local O'Reilly Auto Parts! This fluid also performs extremely well, is buttery smooth, and has shifted very well at temps at around 5 degrees F. IMPORTANT: I don't know if it is a placebo effect- but "the noise" seems to improved. Placebo effect?

Transfer Case: The existing fluid looked good with just a slight brown color and no obvious contamination. It probably didn't need to be changed. Replacement Fluid: Pennzoil Platinum LV Synthetic- in stock and on sale at a local Menards for $4.89/quart! This meets Ford spec and is a very well reviewed fluid.

Draining and filling were easy, and just about anyone with minor mechanical ability should be able to complete a drain/fill. Frankly, it is so easy that really should be no excuse to neglect this important maintenance. Ford is simply WRONG on their fluid change intervals, and if you do the changes yourself, it can be done at a reasonable price using locally sourced fluids that meet OEM specs.

 

[CarbonSteel]

Interesting, do find your T-Case numbers to be typical at 9.5K?

We would need some trending data from a number of transfer cases to establish what would be considered "normal", but in lieu of that, I did not see anything out of the ordinary.

The most important thing that you want to see is the miles per PPM of iron/aluminum/copper increasing which means that less wear metals are being generated per mile which indicates the unit is breaking in and wearing normally.

As a transfer case or axle breaks in (or any non-filtered & non-pressurized equipment), the wear metals should reduce until they hit a steady state which can have some variations, but by and large land within a range.

You can see on my Jeep Wrangler transfer case how the length of run increased but so did the miles per PPM of iron (as an example). This is the trend that you want to see:

 

[Sparkherd]

Change 7MT fluid yesterday. 11,707 miles
Old fluid did not look bad.
A few metal flakes visible in the drain pan, but I've seen worse.
BG Synchro II is some slimy sheeit!!!
Almost 2.8 quarts before the fluid started trinkling out the fill hole.
Tranny is guieter at start up, and much smoother on the road.
I am slightly amazed at how much difference this made.
Oh yeah...I could only get the fill plug back in when the tranny was in Granny Gear; the shifter arm interfered with the fill plug in neutral.
This may not be a problem for those of you with helpers, or the young, but it's PIA to get up off of the floor, and waggle the shifter around, until you can get the fill plug to thread.
Your mileage will probably vary...

 

[vicorjh]

Another rear differential specimen (4K miles):

Front differential. Waste oil in similar condition as to the rear:

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