JLUR Metal Flakes on Diff Housing - How Much is Normal

[gato]

Changed the rear diff cover at ˜500 miles, had normal pasty fine metal on magnetic plug.

Changed front diff cover at ˜3,000 miles (with a few off-road trips in 4HI/4Lo), and found on the mag plug a small amount of metal flakes. Nothing big, but distinct enough pieces like grains of sand sized flakes. Visual inspection showed no scoring or missing metal anywhere. Teeth looked pristine. Fluid looked totally normal otherwise.

Question - is it normal to have a few metal flakes at first diff fluid change? Anything to be concerned? There were maybe 1/2 dozen ˜1/16" sized flakes.

Any help appreciated. This is actually the first time I changed my own diff fluid and aftermarket diff covers.

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[Roky]

Changed the rear diff cover at ˜500 miles, had normal pasty fine metal on magnetic plug.

Changed front diff cover at ˜3,000 miles (with a few off-road trips in 4HI/4Lo), and found on the mag plug a small amount of metal flakes. Nothing big, but distinct enough pieces like grains of sand sized flakes. Visual inspection showed no scoring or missing metal anywhere. Teeth looked pristine. Fluid looked totally normal otherwise.

Question - is it normal to have a few metal flakes at first diff fluid change? Anything to be concerned? There were maybe 1/2 dozen ˜1/16" sized flakes.

Any help appreciated. This is actually the first time I changed my own diff fluid and aftermarket diff covers.

Pic would help, but by description, I’d say your good.

 

[CarbonSteel]

With photos hard to say for sure, but I think you should be fine. Sometimes the manufacturer does not do as good of a job cleaning out the machining swarf as they should and it comes out in the first or second OC.

This is one of the main reasons I say to change the differential oil early in the axle's life. For most axles, the vast majority of the wear happens at 15K miles or less.

PS...since you have a JLUR, you need to do this as soon as you can:

https://www.jlwranglerforums.com/forum/threads/locker-position-sensor-potting-dana-44.59581/

 

[gato]

Pic would help, but by description, I’d say your good.

Stupid, me I didn't take pictures, but basically I ran my finger through the magnetic plug and there was little paste (no surprise given the mileage and the front diff rarely turns), but some sand grains-sized flakes. The gears by appearance looked pristine.

The entire amount was very little. It was just more granular than the rear.

 

[gato]

PS...since you have a JLUR, you need to do this as soon as you can:

https://www.jlwranglerforums.com/forum/threads/locker-position-sensor-potting-dana-44.59581/

I'm not brave enough to do that. I"m rolling the dice that by the time the sensor fails on me I can use the Z-automotive bypass until the sensor becomes available as a replacement part. Finger crossed.

 

[gato]

BTW - my front diff when engaged (4HI or 4LO, locked or unlocked) runs great with no noises or roughness.



Should I plan on pulling the drain plug again after a few more 4WD miles to check? Or is that overkill?

 

[Roky]

Stupid, me I didn't take pictures, but basically I ran my finger through the magnetic plug and there was little paste (no surprise given the mileage and the front diff rarely turns), but some sand grains-sized flakes. The gears by appearance looked pristine.

The entire amount was very little. It was just more granular than the rear.

I think that has to do with how much more the rear is used than the front. There’s more pulverizing so the flakes won’t be as big or as many....... my guess is you’re good.

 

[CarbonSteel]

I'm not brave enough to do that. I"m rolling the dice that by the time the sensor fails on me I can use the Z-automotive bypass until the sensor becomes available as a replacement part. Finger crossed.

At 25K, my rear sensor was half full of oil. The only reason it did not fail is because I had only used it before 10K miles when the oil was not in it or very little had made it inside. Doing something like the potting process is not for everyone, so just be ready with the Z-Automotive Bypass--not a matter of if, but when...

 

[gato]

I think that has to do with how much more the rear is used than the front. There’s more pulverizing so the flakes won’t be as big or as many....... my guess is you’re good.

Thanks, for that - it makes, sense. I'll sleep better.

 

[gato]

At 25K, my rear sensor was half full of oil. The only reason it did not fail is because I had only used it before 10K miles when the oil was not in it or very little had made it inside. Doing something like the potting process is not for everyone, so just be ready with the Z-Automotive Bypass--not a matter of if, but when...

I hear you. Part of my thinking about putting a few hundred miles on the diffs then changing the covers/fluid was to try to get as much of the metal shavings out of the oil.

I assume (but don't know) that it is the metal in the oil, rather than the oil per se, that shorts out the sensor electronics.

I wonder if doing frequent diff fluid changes would decrease the chances of a failure.



P.S. I know that everyone says to clean the diff housing/everything with brake cleaner or such, when changing the cover. Is it possible that the chemicals in the brake cleaner can mess up the sensor seal?
I tried to avoid spraying the sensor, just in case.

 

[CarbonSteel]

I hear you. Part of my thinking about putting a few hundred miles on the diffs then changing the covers/fluid was to try to get as much of the metal shavings out of the oil.

I assume (but don't know) that it is the metal in the oil, rather than the oil per se, that shorts out the sensor electronics.

I wonder if doing frequent diff fluid changes would decrease the chances of a failure.



P.S. I know that everyone says to clean the diff housing/everything with brake cleaner or such, when changing the cover. Is it possible that the chemicals in the brake cleaner can mess up the sensor seal?
I tried to avoid spraying the sensor, just in case.

While the metal shaving increase the conductivity of the oil, the oil itself is conductive (though at a much lower level). I would opine that when the sensor gets to a certain level of oil and is electronically engaged, the PCB contacts make an incorrect connection and it shorts out.

I would also soy that I have changed the oil in my axles perhaps more than anyone on the site (including performing used oil analysis (UOAs) and my sensor still filled with oil (the rear)--it is a seriously piss-poor design by Dana (or more likely specifications from FCA). The front is typically not an issue (at least in the short term) simply due to the lower levels of use versus the rear.

DO NOT use brake cleaner inside the axle. The solvents can attack the seals and cause you to have a leak that can be expensive to repair. It can also break down the gear oil and reduce your protection. A clean LINT FREE cloth is the best way to clean out the axle housing. With that said, I cleaned mine in this manner (lint free cloth) at my initial oil change and not much came out of the housing.

Where the metal tends to build up is between the locking sensor and the locking plate. When I removed mine to pot them, they were loaded with metal filings.

Hope this helps!

 

[gato]

While the metal shaving increase the conductivity of the oil, the oil itself is conductive (though at a much lower level). I would opine that when the sensor gets to a certain level of oil and is electronically engaged, the PCB contacts make an incorrect connection and it shorts out.

I would also soy that I have changed the oil in my axles perhaps more than anyone on the site (including performing used oil analysis (UOAs) and my sensor still filled with oil (the rear)--it is a seriously piss-poor design by Dana (or more likely specifications from FCA). The front is typically not an issue (at least in the short term) simply due to the lower levels of use versus the rear.

DO NOT use brake cleaner inside the axle. The solvents can attack the seals and cause you to have a leak that can be expensive to repair. It can also break down the gear oil and reduce your protection. A clean LINT FREE cloth is the best way to clean out the axle housing. With that said, I cleaned mine in this manner (lint free cloth) at my initial oil change and not much came out of the housing.

Where the metal tends to build up is between the locking sensor and the locking plate. When I removed mine to pot them, they were loaded with metal filings.

Hope this helps!

Yes. It helps a lot. Thanks so much for taking the time to answer.

It never felt right to me that every Youtube video on changing the diff cover bathes everything with brake cleaner. I did it against my better judgement and kept only to the lower part of the diff housing. Wish I had gotten your insight before doing it.

 

[CarbonSteel]

Yes. It helps a lot. Thanks so much for taking the time to answer.

It never felt right to me that every Youtube video on changing the diff cover bathes everything with brake cleaner. I did it against my better judgement and kept only to the lower part of the diff housing. Wish I had gotten your insight before doing it.

Did you let it dry completely before closing it back up and wiped it out too?

 

[gato]

Did you let it dry completely before closing it back up and wiped it out too?

Yes, sir - Spray (little). Wiped. Air dry. Took my time putting the cover back on. Refilled. Immediately drove in 4HI to get gear oil to bathe everything. Activated lockers, etc.

I also make it a habit to put it in 4HI every now and then and cycling the lockers to get everything turning and actuating in the front.

 

[CarbonSteel]

Yes, sir - Spray (little). Wiped. Air dry. Took my time putting the cover back on. Refilled. Immediately drove in 4HI to get gear oil to bathe everything. Activated lockers, etc.

I also make it a habit to put it in 4HI every now and then and cycling the lockers to get everything turning and actuating in the front.

It should be fine. I would put some miles on it and change it again. I changed mine at 5K miles, again at 10K miles, then once more at 25K miles. What one would expect to see (a tapering off of iron in the oil) does not seem to happen with these axles. This behavior may be attributed to gear design and metallurgy, reduced oil capacity from previous generations, and increased operating temperatures from previous generations.

To put it into context, I had a Ford F-150 FX4 with a 9.75" rear locking differential that I towed between 8-9K pounds for 45% of the 160K miles that I had it. In its 160K miles it produced a total of 697PPM of iron. My Rubicon has produced more than 3x that amount in 26K miles.

Here are the UOAs for my Rubicon rear axle:

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