I will preface this by saying – Ladies and Gentlemen, check your axle drain plugs (at least on a Jeep)!! I have 5K miles on my Rubicon and I could have easily removed these drain plugs with a ¼” finger ratchet. They were not tight at all and no way would they have remained in the axle for 50 or 75K miles without loosening and falling out.

Phase 1 of my project (installing axle temperature gauges--front and rear) is now completed and the covers with the temperature bosses are now installed. I have some stainless cap screws on the way to take the place of the OEM hex heads. The next step will be installing the gauges and wiring.

I did not find any surprises in either axle which are Dana 44 HD models (M210 in the front and M220 in the rear--these are the new generation Dana axles and both are electronic lockers), though I am not thrilled with how little capacity there is in each axle (1.25QTs in the front and 1.5QTs in the rear) and I will change the fluid on a fairly conservative OCI. The vast majority of axle wear occurs during the first 15K miles and despite longer and longer runs, the wear metals will continue to drop and true to that statement, I found a fair amount of metal on the magnetic drain plugs on both axles, but more (as expected) on the rear.

The rear axle oil was very dark and loaded with metals (you can see a video of the oil here) - . I believe the rear axle had synthetic 75W-140 (should be anyway since I have the towing package) in it as it appeared to be more viscous than the front axle which was specified to be a conventional 85W-90.

The front axle oil was honey colored and this was expected since front axles rarely see the amount of use that a rear one will and mine (at least to this point) aligns with that premise.

Amsoil Severe Gear was installed in both axles with 75W-140 in the rear and 75W-110 in the front. I did not install 75W-90 because 75W-110 is the upper viscosity that 75W-90 used to be before the SAE J306 tables were updated some time ago.

UOAs of both axles will be done to set a baseline to compare against future OCs and both axles will only see Amsoil going forward as I have had excellent results with that oil especially when towing.

Here are some photos – enjoy!

Front Drain Plug:


Rear Drain Plug:


Clean Drain Plug (For Reference):


Front Axle Internals:


Rear Axle Internals:


Rear Axle Oil:


Front Axle Completed (with temperature sensor boss at top of cover):


Rear Axle Completed (with temperature sensor boss at top of cover):

Nice!!

I'll have to think about doing mine, almost 10K on it. Reusable cover gasket from factory?

Yes: it is rubber encapsulated steel. When I removed the last bolt on the rear cover it fell off. I was not expecting that, as most covers have to be pried off.

Based upon the condition of my oil at 5K, I would definitely change it.

Why would the rear diff fluid be so contaminated? Any chance water got in the diff?

No water, this is normal in every axle I have owned. The caveat is that most people do not dump the fluid this early and so they never see it until tens or hundreds of thousands miles later.

Nearly all axle wear occurs at 15K miles or less.

Thank you for posting. I'll give my truck another change around 100K miles. I think I won't change again in the truck again after this.

My Gladiator gear fluid looked the same way front/rear when I changed out the fluid and installed new covers also at 5K miles.

The muddy grey swirl consistency of the fluid is normal on the first change and is just a mixing of the gear oil and the gear paint compound they used when they set the ring gear and pinion gear lash.

With the amount of metal on the drain plug and in the oil, I am not so sure that paint compound is the root cause of the color. First OCs always have a lot of metal caused by the mating of the gears during wear in.