What is the good differential fluid for first change?

[2nd 392]

I run conventional 85W-140 in my axles to break them in--as many gear and after market axle manufacturers recommend, however, the problem with conventional oil is cold weather and the OP is from Alaska. I would not run conventional oil in the temperatures that he is likely to see.

In addition (and no disrespect to any vendor that recommends using conventional oil), but there are millions of axles that come from the factory with synthetic gear oil. Short of a poor design, these axles last hundreds of thousands of miles with no issues running synthetic oil.

Below is a video that compares conventional gear oil versus synthetic in extremely cold weather.

From the video, according to SAE J306, here are the lowest temperatures these viscosities can be used:

75W-XXX = -40°C or -40°F
80W-XXX = -26°C or -14.8°F
85W-XXX = -12°C or +10.4°F

After break in do you use synthetic? Regear Monday, little time to decide. Also- having Jeep do the install in hopes of less warranty issues ( ) , do you happen to know if the recommended non-synthetic Lucas meets factory standards? Thanks. Edit- or the best synthetic that does?

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[Rodeoflyer]

don't overthink it..

 

[6.2Blazer]

I am definitely not an Amsoil shill, but their gear oil is some of the very best on the market and it is absolutely better than OEM Mopar in every way possible.

I towed heavy in a 2010 FX4 for 45% of the 160K miles that I put on it and the thing that impressed me the most about it was the viscosity retention. After 80K miles on a run, it retained 93% of the initial viscosity. The person in that example should have pushed a lot harder on FCA to prove that Amsoil was the root cause of the failure--highly doubtful.

What? How did you test for viscosity retention? What is the expected "visconsity retention" of any other gear lube? Did you test any other gear lube under the exact same conditions?

 

[CarbonSteel]

What? How did you test for viscosity retention? What is the expected "visconsity retention" of any other gear lube? Did you test any other gear lube under the exact same conditions?

It is not that difficult. You have to take a virgin sample and test it, then take the used sample and test it and then compare.

You can see below that Motorcraft retained less viscosity in less miles than the Amsoil--of course, this is a very small sample set. With that said, I have collaborated with many different people (lubrication and axle engineers) through the years and though it is anecdotal from me to all of you, there are many oils that do not retain viscosity in the 90 percentile at 80K+ miles.

Obviously, there are a number of factors that impact viscosity retention--axle design, load, operating temperatures, lubrication composition and the like. Ring and pinion gears by their very nature have shearing forces and that shearing is the primary root of why viscosity loss occurs in an axle.

 

[CarbonSteel]

After break in do you use synthetic? Regear Monday, little time to decide. Also- having Jeep do the install in hopes of less warranty issues ( ) , do you happen to know if the recommended non-synthetic Lucas meets factory standards? Thanks. Edit- or the best synthetic that does?

Yes; I do switch from conventional to synthetic after break-in. The caveat with these Dana 44 Advanteks is they generate a lot of metal even after the initial break-in so I typically make 3 runs on conventional--500 miles, 1,500 miles, 3000 miles, then switch to synthetic at 5K.

Mopar's specification on gear oil is not proprietary (thank goodness) and by that I mean if the oil meets GL-5 specifications, you are good to go. Both Lucas 85W-90 and 85W-140 (as well as their synthetics) meet GL-5.

 

[2nd 392]

Yes; I do switch from conventional to synthetic after break-in. The caveat with these Dana 44 Advanteks is they generate a lot of metal even after the initial break-in so I typically make 3 runs on conventional--500 miles, 1,500 miles, 3000 miles, then switch to synthetic at 5K.

Mopar's specification on gear oil is not proprietary (thank goodness) and by that I mean if the oil meets GL-5 specifications, you are good to go. Both Lucas 85W-90 and 85W-140 (as well as their synthetics) meet GL-5.

Your knowledge by experience appreciated! Thanks

 

[2nd 392]

Yes; I do switch from conventional to synthetic after break-in. The caveat with these Dana 44 Advanteks is they generate a lot of metal even after the initial break-in so I typically make 3 runs on conventional--500 miles, 1,500 miles, 3000 miles, then switch to synthetic at 5K.

Mopar's specification on gear oil is not proprietary (thank goodness) and by that I mean if the oil meets GL-5 specifications, you are good to go. Both Lucas 85W-90 and 85W-140 (as well as their synthetics) meet GL-5.

Forgive me for being a pest, but isotropic finish, still recommended 2 additional break in changes ?

 

[CarbonSteel]

Your knowledge by experience appreciated! Thanks

To help with some of the context. I have tested the gear oil in my rear axle through 3 re-gears for a total of 15 times thus far or about 5 per re-gear (obviously, I did not start off thinking that I would re-gear 3 times).

For the factory gears, I opted to change it the first time at 5K assuming that these Dana axles would be comparable to a Ford 8.8/8.75 or GM 10 bolt. Errr...not and so for the re-gears I changed it earlier and more frequent until I hit 5K.

With that said, if you look at the image below:

- I changed the factory fill at 5K miles, the iron was 604

- I sampled it at 10K miles (5K on the oil), again at 15K miles (now 10K on the oil) and again at 20K miles (now 15K on the oil). The iron is dropping and was reduced from the 5K sample, but it was still very high compared to other axle brands of the same type--296, 379, and 466PPM.

- I then changed it at 20K miles and sampled at 25K miles (5K on the oil) and sampled one last time before I re-geared the first time at 26K (6K on the oil). The iron as 199 and 219PPM.

- Compare these results to those I posted earlier on the 2010 FX4 I had and you can see why I say these axles generate a lot of iron and that most axles generate the majority of their wear metals in 15K miles or less. The FX4 generated 429PPM at 13K, another 148PPM from 13K to 56K, and only 120PPM from 56K to nearly 160K. If our axles behaved like the Ford, we would not have so many issues with failed locking sensors and likely less failed LSD axles.

 

[CarbonSteel]

Forgive me for being a pest, but isotropic finish, still recommended 2 additional break in changes ?

Not a pest at all. The Isotropic polished gears require zero heat cycles, but you definitely need to change the oil at 500 miles. I probably am in overkill mode, but oil is cheap and axles are not.

ChevyMitchell did my 5.13 re-gear with polished gears and I changed my oil every 500 miles or 3x on the way home from NC to CO. I used Valvoline conventional 85W-140 which was about $7.00 on sale at WalMart, so I was not concerned about the cost.

You would be fine with a single oil change at 500 if you wanted to only do that because the other benefit of the polishing is they generate a lot less iron than non-polished.

Black oxide covers all manner of sins on non-polished gears

@2nd 392 - to help visualize, here are the UOAs for the 4.88s I had that were Isotropic polished. Vast difference from the OEM non-polished:

 

[2nd 392]

Not a pest at all. The Isotropic polished gears require zero heat cycles, but you definitely need to change the oil at 500 miles. I probably am in overkill mode, but oil is cheap and axles are not.

ChevyMitchell did my 5.13 re-gear with polished gears and I changed my oil every 500 miles or 3x on the way home from NC to CO. I used Valvoline conventional 85W-140 which was about $7.00 on sale at WalMart, so I was not concerned about the cost.

You would be fine with a single oil change at 500 if you wanted to only do that because the other benefit of the polishing is they generate a lot less iron than non-polished.

Black oxide covers all manner of sins on non-polished gears

@2nd 392 - to help visualize, here are the UOAs for the 4.88s I had that were Isotropic polished. Vast difference from the OEM non-polished:

A LOT LESS!! From your numbers it appears that two break in changes would be worthwhile. Then synthetic. Your experience has saved me much agonizing over what to do, greatly appreciated!

 

[2nd 392]

Not a pest at all. The Isotropic polished gears require zero heat cycles, but you definitely need to change the oil at 500 miles. I probably am in overkill mode, but oil is cheap and axles are not.

ChevyMitchell did my 5.13 re-gear with polished gears and I changed my oil every 500 miles or 3x on the way home from NC to CO. I used Valvoline conventional 85W-140 which was about $7.00 on sale at WalMart, so I was not concerned about the cost.

You would be fine with a single oil change at 500 if you wanted to only do that because the other benefit of the polishing is they generate a lot less iron than non-polished.

Black oxide covers all manner of sins on non-polished gears

@2nd 392 - to help visualize, here are the UOAs for the 4.88s I had that were Isotropic polished. Vast difference from the OEM non-polished:

Pest again— Jeep won’t have non synthetic so I will take it with the gears, but the manual doesn’t give capacity, how much do I need?

 

[CarbonSteel]

Pest again— Jeep won’t have non synthetic so I will take it with the gears, but the manual doesn’t give capacity, how much do I need?

You need about 1.3QTs for the front and 1.6QTs for the rear. I would bring 4 QTs and you'll be covered.

 

[Viking Jeeper]

Currie Enterprises recommends non-synthetic gear oil in differentials.
I’m not sure but think they’ve built a few diffs over the years

Currie sure had built a few diffs over the years but not as many as Jeep. Jeep recommends their synthetic 75w85.

 

[Jtclayton612]

Currie sure had built a few diffs over the years but not as many as Jeep. Jeep recommends their synthetic 75w85.

and Dana actually recommends synthetic 75w-140 in their axles, against what jeep says iirc.

 

[Vinman]

Currie sure had built a few diffs over the years but not as many as Jeep. Jeep recommends their synthetic 75w85.

And Currie cares more about building, strong, long lasting differentials than the best possible fuel economy.

And do you ever notice that Jeep and Dodge seem to always recommend a more expensive, oddball gear oil weight as opposed to a more available oil?

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