75w85 rear differential gear oil what are you using

[redone17]

@CarbonSteel - any German (or otherwise) Ford approved synthetic gear oil?

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[CarbonSteel]

@CarbonSteel - any German (or otherwise) Ford approved synthetic gear oil?

Differentials are a bit different (at least from my experience). First of all, I would not run a "weird" viscosity like 75W-85, I would run a 75W-90, 75W-110, or 75W-140--but obviously, this is something that each person must decide. I have a lot of experience with the rear axle in the Bronco because it is the same axle that is in the Jeep Wrangler. Dana specifies 75W-140 in the front and rear of the Dana 44 Advantek whereas the OEMs reduce that in the quest for more MPG. These axles run hotter than previous generations and typically have less oil capacity, though Ford has more sense than Jeep in that area and specified about 2QTs in the rear versus Jeep specifying 1.6QTs in the rear.

Next, they generate more metal than any other axle I have experience with and generate it for far longer than say a Ford branded axle like a 9.75" or a 10.25" axle. From my experience, most Ford branded axles are fully broken in by 15K miles and from that point out produce less and less wear metals per mile. The Advanteks are not like that--they keep producing a substantial amount of metal for longer. Hence, I would change the oil in the axles no later than 5K miles and for the rear, would change it again at 10K, and once again at 15K to get all of the wear metals out.

The Jeep Dana 44 axles had serious issues with failing locking differential modules and until recently did not sell it as a spare part, when it failed, the entire axle was replaced. I have not seen anyone on this forum complaining about that for Broncos, so I will assume that Ford had more sense in that area as well and epoxy potted the sensor to prevent the oil from contamination and ruining it.

Now to the oil, Ford is specifying a conventional oil in the front axle (80W-90) and a synthetic in the rear (75W-85). The API specification for gear oil is API GL-5 and I feel confident and comfortable with using a GL-5 specified oil versus the Ford specification (but I am not recommending that anyone take my advice). For me, I will probably run 75W-110 in the front and rear of my Wildtrak. 75W-110 is the upper viscosity that 75W-90 used to be before the SAE J306 tables were redefined to split the 75W-90 range into two ranges. I feel equally confident in saying that if someone is towing with their Bronco, they should be using 75W-140 in the rear axle as Dana specifies.

As to oil choices, for 75W-110 it is limited to a few brands whereas 75W-90 or 75W-140 are very common. Castrol, Mobil 1, or Valvoline are all good off the shelf choices for those two viscosities.

Hope this helps!

 

[CarbonSteel]

Jeep requires the same fluid on their D44s, so it must be a Dana thing.

A lot of Jeep people run 90 with no issues.

I won’t try convincing anyone. I just use 90 because it is more common and I like the squeez packs.

Dana specifies 75W-140 in their Dana 44 Advanteks. The OEMs reduce the viscosity chasing CAFE credits (MPG).

 

[redone17]

Dana specifies 75W-140 in their Dana 44 Advanteks. The OEMs reduce the viscosity chasing CAFE credits (MPG).

Why are Dana & Ford’s specs so wildly different?

 

[scotman623]

Why are Dana & Ford’s specs so wildly different?

To make it get better MPG to keep big brother happy.. I run Royal Purple.

 

[swamp2]

Although this thorough gear oil test was generated by AMSOIL, I still believe it to be unbiased. Its by far the most quantitative product comparison I've ever seen. I'm also not sure I agree with their equal weighting across criteria. Top results were AMSOIL and Mobil 1. Redline also did well in all of the pressure/wear tests, which are IMHO the most important ones.

 

[CarbonSteel]

Why are Dana & Ford’s specs so wildly different?

CAFE credits (MPG). In theory, heavier oil creates more drag and reduces MPG. Your right foot or a head wind will impact MPG more than a viscosity change ever will.

 

[CarbonSteel]

Although this thorough gear oil test was generated by AMSOIL, I still believe it to be unbiased. Its by far the most quantitative product comparison I've ever seen. I'm also not sure I agree with their equal weighting across criteria. Top results were AMSOIL and Mobil 1. Redline also did well in all of the pressure/wear tests, which are IMHO the most important ones.

Not to come off as an Amsoil fan boy, but they make arguably the best gear oil on the market (motors oils not so much).

Severe Gear is top notch oil.

 

[Langwilliams]

My '19 Ranger had drain plugs for the diffs, no need to remove the cover. Ford really cheaped out getting rid of them.

 

[da_jokker]

My '19 Ranger had drain plugs for the diffs, no need to remove the cover. Ford really cheaped out getting rid of them.

Well they did give you reusable gaskets instead. Maybe the idea was to pull the cover off so you could actually see (and clean out) instead of just a drain and fill?

 

[Langwilliams]

Well they did give you reusable gaskets instead. Maybe the idea was to pull the cover off so you could actually see (and clean out) instead of just a drain and fill?

I think they were the same gaskets. I assume it's for if you want to do a quick change after a water crossing not for changing after a long service interval.

 

[redone17]

Although this thorough gear oil test was generated by AMSOIL, I still believe it to be unbiased. Its by far the most quantitative product comparison I've ever seen. I'm also not sure I agree with their equal weighting across criteria. Top results were AMSOIL and Mobil 1. Redline also did well in all of the pressure/wear tests, which are IMHO the most important ones.

This was massively informative. Thanks for sharing.

 

[redone17]

Any downside to running synthetic in front? I wonder why Ford suggests otherwise.

 

[CarbonSteel]

Any downside to running synthetic in front? I wonder why Ford suggests otherwise.

None--synthetic oils handle heat and cold far better than conventional oils ever will.

 

[CarbonSteel]

Although this thorough gear oil test was generated by AMSOIL, I still believe it to be unbiased. Its by far the most quantitative product comparison I've ever seen. I'm also not sure I agree with their equal weighting across criteria. Top results were AMSOIL and Mobil 1. Redline also did well in all of the pressure/wear tests, which are IMHO the most important ones.

Meant to comment earlier on this one. I agree despite Amsoil "hosting" the test that it was objective as much as it could be and Amsoil called it out when it could not be such as the filter patch test.

Also, the overall test results for both Red Line and Royal Purple were not as good as Mobil 1 and Castrol. I highlight this because both RL and RP tend to be the "darlings" in most automotive forums along with Amsoil.

It is an important highlight because it shows that off the shelf oils such as Mobil 1 and Castrol can perform as well if not better than boutique oils like RL and RP at less cost and thus there is no need to chase such oils as there is no marked difference except increased cost for less performance.

I have tried many of the oils in the list, but for axles that are heavily worked or have design issues (such as the AAM axles that were under certain Dodge 2500 and 3500 trucks for a number of years), I gravitate back to Amsoil.

With that said, I have also put hundreds of thousands of miles on axles using Mobil 1 with no issues whatsoever. Lots of choices out there, but test results like this help make an informed one.

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