Differential oil

[-lenny-]

Am I reading this correctly, that if I use an aftermarket 75w140 like Amsoil, or other synthetic, I do not need to add friction modifier?

Sponsored

 

[g2020]

There is thread somewhere on this forum that goes pages after pages talking about this. I will be putting -140 on both diffs, that spec comes from Dana. Same Valvoline one, easier to pour

If you come across a Dana document with the SAE 75W-140 spec for a new axle, please DM it to me. I maintain a post on Key Info and will change the guidance in my post if I am convinced. A single doc with a blanket statement for all (new and rebuild) solid axles on the JL/JLU/JT will be best, but multiple docs will also work.

The Rebuild Specification (posted by Hootbro) from Spicer/Dana calls for 75W-140. To avoid restarting debates, I have a supporting doc for everything I write. I need a doc that says "new" or "all".

After all is said and done, it is up to each owner whether to follow the owner's manual, or advice from experienced owners who have a different opinion.

 

[g2020]

Am I reading this correctly, that if I use an aftermarket 75w140 like Amsoil, or other synthetic, I do not need to add friction modifier?

Correct. Friction modifier or limited-slip (LS) additive needs to be stated on the bottle or on the manufacturer's website. Extra friction modifier can be required in some cases. You'll know if you need it. Some folks add an ounce (literally) of MOPAR 04318060AD friction modifier for good measure, but I don't. Also see the table in section 1.3 of my post on Links to Prices.

 

[CarbonSteel]

Dana specifies 75W-140 for all Mxxx series axles used in the Jeep JL:

M186 Front - https://d3qx1uccksbb2n.cloudfront.net/docs/SPECSHEET-JL-FRONT-D30-42019.pdf

M200 Rear - https://d3qx1uccksbb2n.cloudfront.net/docs/SPECSHEET-JL-REAR-D35A-42019.pdf

M210 Front - https://d3qx1uccksbb2n.cloudfront.net/docs/SPECSHEET-JL-FRONT-UD44A-42019.pdf

M220 Rear - https://d3qx1uccksbb2n.cloudfront.net/docs/SPECSHEET-JL-REAR-UD44A-D44A-42019.pdf

There is only one reason Jeep recommends a lower viscosity oil than Dana and longevity is not part of that decision.

 

[WannFly]

If you come across a Dana document with the SAE 75W-140 spec for a new axle, please DM it to me. I maintain a post on Key Info and will change the guidance in my post if I am convinced. A single doc with a blanket statement for all (new and rebuild) solid axles on the JL/JLU/JT will be best, but multiple docs will also work.

The Rebuild Specification (posted by Hootbro) from Spicer/Dana calls for 75W-140. To avoid restarting debates, I have a supporting doc for everything I write. I need a doc that says "new" or "all".

After all is said and done, it is up to each owner whether to follow the owner's manual, or advice from experienced owners who have a different opinion.

See the post above from @CarbonSteel , he knows about oil, way more than I will ever know.

As you correctly pointed out, it's up to the owner. His / Her diff, his / her choice. I would rather go by the manufacturer (Dana) recommendation than the assembler's (Jeep) recommendation.

 

[jadmt]

yet when you call dana and ask what to use they will refer you to jeep's recommendations which is 75w85...Which begs the question of there is a failure inside the warranty period does Jeep bill it back to Dana spicer or does jeep eat it?

 

[Terrymo]

I’m not a subject matter expert on anything. I’m continually baffled by folks vying to be the newest forum subject matter experts on battery and oil topics in particular.

 

[CarbonSteel]

yet when you call dana and ask what to use they will refer you to jeep's recommendations which is 75w85...Which begs the question of there is a failure inside the warranty period does Jeep bill it back to Dana spicer or does jeep eat it?

I have spoken to multiple Dana engineers and have never had such a recommendation. The other point is that Jeep would have to PROVE that higher viscosity oil caused the failure. In all of my 40 years of working on vehicles and participating in many forums/discussions, I have never heard of a case where a higher viscosity oil caused a failure--not once.

 

[jadmt]

I have spoken to multiple Dana engineers and have never had such a recommendation. The other point is that Jeep would have to PROVE that higher viscosity oil caused the failure. In all of my 40 years of working on vehicles and participating in many forums/discussions, I have never heard of a case where a higher viscosity oil caused a failure--not once.

I am not saying there is an issue with the higher viscosity...I am referring to the lower viscosity that jeep recommends..is jeep eating or is dana...Dana recommended to me to use what jeep recommends, so that is why I am curious who pays if there is a failure, not that I have read too many on jeeps other than a couple of posts on here with people who have had the factory 4.88 fail.

 

[CarbonSteel]

I am not saying there is an issue with the higher viscosity...I am referring to the lower viscosity that jeep recommends..is jeep eating or is dana...Dana recommended to me to use what jeep recommends, so that is why I am curious who pays if there is a failure, not that I have read too many on jeeps other than a couple of posts on here with people who have had the factory 4.88 fail.

Again--Jeep would have to prove the higher viscosity oil caused the failure. Otherwise, Jeep is eating the repair. They will not be able to do so--there are ZERO parts in an axle that are viscosity dependent and higher viscosity oils equal more protection, not less.

In addition, they have a conflict on two fronts:

1. Dana specifies 75W-140 in all Mxxx axles.
2. Jeep recommends 75W-140 in at least one of the Mxxx axles. It is not a far stretch to defend that use in all Mxxx axles.

 

[jadmt]

Again--Jeep would have to prove the higher viscosity oil caused the failure. Otherwise, Jeep is eating the repair. They will not be able to do so--there are ZERO parts in an axle that are viscosity dependent and higher viscosity oils equal more protection not less.

In addition, they have a conflict on two fronts:

1. Dana specifies 75W-140 in all Mxxx axles.
2. Jeep recommends 75W-140 in at least one of the Mxxx axles. It is not a far stretch to defend that use in all Mxxx axles.

again i am not talking about the higher weight I am curious about the lower weight......if dana recommends 75w140 and jeep uses 75w85 is it totally on jeep or does jeep put it back on dana...take the 75w140 out of the discussion completely....I am solely wondering about the recommended 75w85. again have not read about a lot of factory gearsets failing other than a few jk spider gears and some 4.88 factory installed gears..

Personally i would run either one without worrying. I have run mopar 75W85 in all the rigs I have that call for it and never an issue but would not worry if I ran 75w140 either.

 

[CarbonSteel]

again i am not talking about the higher weight I am curious about the lower weight......if dana recommends 75w140 and jeep uses 75w85 is it totally on jeep or does jeep put it back on dana...take the 75w140 out of the discussion completely....I am solely wondering about the recommended 75w85. again have not read about a lot of factory gearsets failing other than a few jk spider gears and some 4.88 factory installed gears..

Jeep eats it. The axles are factory filled with 75W-85 and provided the axle was not overloaded or used in "unapproved" conditions and if the oil causes a failure, that is 100% on Jeep.

 

[JMM]

I went through this a while back and read the 75-140 was recommended for the rear when the vehicle is used frequently for towing. I've built many axles in the last 20 years and never had a failure due to the lube used. I feel lube level is at least as important as lube weight assuming you're in the 75-85/90 ballpark. People have overfilled their diffs and done damage due to aeration and the lack of slinging the oil to the bearings and pinion.

 

[jadmt]

Jeep eats it. The axles are factory filled with 75W-85 and provided the axle was not overloaded or used in "unapproved" conditions and if the oil causes a failure, that is 100% on Jeep.

that has been my point all along, they must have at least a little faith in what they recommend then.

 

[CarbonSteel]

that has been my point all along, they must have at least a little faith in what they recommend then.

They reduced the capacity and the viscosity to increase MPG (CAFE) which is not conducive to longevity. We also must note that:

1. Jeep only has to worry for 60K miles.
2. Most Jeep owners drive them normally and do not modify them.
3. If memory serves, Jeep recommends 75W-140 for towing, so they also are "silently" acknowledging that 75W-85 is not adequate for anything but driving.
4. The manufacturer of the axle does not recommend 75W-85.

In the end, one must do what suits them best. I will take Dana's recommendations over FCA/Stellantis any day of the week.

Sponsored