2019 Jeep Rubicon F&R Axle UOAs [5,000 Miles]

[CarbonSteel]

Here are the UOA results from Polaris for the Dana 44 front and rear axles of my Rubicon (M210 Front and M220 Rear). The viscosity of the oil indicates the factory fill was 80W-90 in both. I would have expected the rear to have 75W-140 in it since I have the towing package and Jeep recommends that oil for towing.

Although I have not used 4x4 mode yet, the front axle had some iron in the oil simply due to the design where the axle shafts spin in 4x2 mode, but the ring and pinion do not. The front axles on the Rubicon have a disconnect built-into them.

I have to say the UOA for the rear axle is the worst I have ever seen with regards to PPM of iron for such low mileage. For only 5,000 miles, it was a surprise to see 604PPM of iron. To put it into context, the cumulative iron for 150,000 miles in my 2010 FX4 (which had towed 8-9K pounds for at least 60,000 of those miles in temperatures ranging from -22°F to +117°F in the desert and mountains) was 697PPM of iron. With that said, these results support the concept that most axle wear occurs at 15K miles or less and it seems the Dana axle is no different.

The oil was fairly acidic with a TAN in the 1.47 to 1.81 range, but without a VOA of the oil to use as a comparison, it will not be possible to know if this is abnormal. However, most gear oil is somewhat acidic, for example, a VOA of Amsoil 75W-140 I performed found the TAN of the oil to be 3.1. As shown in this thread - 2019 Jeep Rubicon Axle OC [5,000 Miles], I picked up a second set of OEM front and rear covers from a fellow Jeep enthusiast and welded in a 1/8" NPT threaded boss into the top of the cover so that I can install a set of ISS Pro temperature gauges to monitor axle temperatures.

Viscosities for both oils are within specification and nothing else abnormal jumped out at me. I will be keeping an eye on the iron and may perform another UOA in a few thousand miles to ensure the iron is trending downwards as should be expected. 1.3QTs of Amsoil 75W-110 was installed in the front axle and 1.5QTs of Amsoil 75W-140 was installed in the rear. I will certainly not be performing any extended oil changes with the small capacity of these axles.

Enjoy!

 

[Sunnyinhollister]

When did the Rubicon get the front axle disconnects?

 

[panthermike]

Thanks for sharing, that does seem like a lot of FE for the rear axle, good call changing it early. My Ram is at 14,XXX and I think I'll do the diffs sooner rather than later!

 

[Snagglefoot]

Excellent post. Thanks.

 

[CarbonSteel]

Originally Posted by Sunnyinhollister
When did the Rubicon get the front axle disconnects?
In 2017 with the debut of the JL series.

 

[dareo]

Cool info. Another great contribution 2015_PSD

 

[totegoat]

Thanks for taking the time.

 

[CarbonSteel]

Another update to the thread; here is the UOA for the rear axle at 15K miles on the axle and 10K miles on the Amsoil 75W-140. I did not change it and am currently on a road trip and should have another 5K on it soon.

A few things to note:

1. The oil is thickening slightly from the last UOA (23.1 vs 22.8)
2. The TAN (total acid number) is slightly lower meaning the oil is becoming more acidic, but the virgin TAN for the oil is 3.1 so it is not a concern for me yet.
3. The iron production has dropped significantly only producing 83 PPM for this 5K run versus 296 PPM for the prior one.

Enjoy!

 

[The Critic]

Thanks for posting. Based on this information, most of the wear occurred during the first 10K miles on your differentials. With this new knowledge, performing the first change at 10K instead of 5K may be a good idea.

 

[demarpaint]

Thanks for sharing. After 10k miles on the FF in my 2016 Rubicon went with Mobil 1 75w90 in the front and 75w140 in the rear. According to the research I did it was fine for severe service. Everything is nice and quiet after about 10K miles on the lubes. No hit in mpg that I could measure over the factory fill.

 

[CarbonSteel]

Thanks for posting. Based on this information, most of the wear occurred during the first 10K miles on your differentials. With this new knowledge, performing the first change at 10K instead of 5K may be a good idea.

604PPM of iron happened in the first 5K and iron generation reduced exponentially each time after that.

Since the oil system is not pressurized or filtered, I have often wondered if more wear occurs with contaminant laden oil. For example, would there only be 296PPM of iron generated from 5K to 10K or would it have been much more had I not changed it.

Oil temperatures are another consideration for gauging OCI. At 70MPH, I see 200°F all day, at 75MPH, I see 205°F-210°F most of the time, and at 75+MPH, I see 221°F-225°F.

Since I believe that my axle is now fully broken in (at least until I regear), I plan to use the UOA information in combination with the temperature guide below to aid me in determining when to change the oil.

Temp Reference Chart – oil change frequency
o 170 Deg - 100,000 Miles
o 200 Deg - 50,000 Miles
o 220 Deg - 25,000 Miles
o 240 Deg - 12,000 Miles
o 260 Deg - 5,000 Miles
o 260-300 Deg – 500-1000 Miles until Temp is controlled

Here is the next UOA, the oil was changed at 20K and Amsoil 75W-140 reinstalled:

 

[Brons2]

Doesn't appear to me that it was in need of changing. Will be interesting to see next OCI.

 

[CarbonSteel]

Doesn't appear to me that it was in need of changing.

Based on?

 

[4WD]

Based on?

After my 3k gear oil looked so bad … ran another 4k and changed again. Both magnets loaded.
Front had Mobil 1 75w90 … normally a very clear oil … rear had Valvoline SynGear 75w140.
Filled both with conventional Valvoline 75w140 … “thicky n sticky” (and stinky) for sure !
Will run that this summer and see.

Front and rear with just 4k

 

[CarbonSteel]

After my 3k gear oil looked so bad … ran another 4k and changed again. Both magnets loaded.
Front had Mobil 1 75w90 … normally a very clear oil … rear had Valvoline SynGear 75w140.
Filled both with conventional Valvoline 75w140 … “thicky n sticky” (and stinky) for sure !
Will run that this summer and see.

Front and rear with just 4k

These axles are iron shredders for sure. I had an interesting conversation with GearFX when I sent my new 4.88 gears to be REM Isotropic polished and they opined that heat in combination with the overall metallurgy and the new gear design is the root cause of the iron generation. I am waiting for my shop to have an opening to get mine re-geared and cannot wait to see if the polishing shortens the break-in and produces less metals than the OEM set.

One thing is for sure, extended OCIs in these axles can almost guarantee a short life...

 

[IndyFan]

These axles are iron shredders for sure. I had an interesting conversation with GearFX when I sent my new 4.88 gears to be REM Isotropic polished and they opined that heat in combination with the overall metallurgy and the new gear design is the root cause of the iron generation. I am waiting for my shop to have an opening to get mine re-geared and cannot wait to see if the polishing shortens the break-in and produces less metals than the OEM set.

One thing is for sure, extended OCIs in these axles can almost guarantee a short life...

My last change, which was my 2nd, I felt the gear lube looked a bit better and had significantly less shavings, even though it still had a lot for 15k on it. But I think its getting better. I'm running Mobil 1 this time around and will see how it looks after the next 15k are complete. I've got about 5 or 6k on it right now.