Is the factory fill of the diffs and transfer case Synthetic oil?

[Troybilt]

So I was told this stuff is fine for my 2020 JTR front diff. Is that good info?

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[Hootbro]

Tell that to the jug of 75W-85 gear lube I’ve got sitting in my garage.

Kevin

Brand? Got a pic?

 

[Renegade]

All 75W-85 grade gear oils are synthetic.

Really? I didn’t know that. I’ve got two jugs of 75w-90 in my garage, and one is synthetic, and the other is conventional. What about this stuff?

 

[Kevin_D]

Brand? Got a pic?

I don’t remember the brand, and can’t get a picture.
But it smells just as nasty as any gear lube I’ve used over the past 50 years.

Kevin

 

[Hootbro]

Really? I didn’t know that. I’ve got two jugs of 75w-90 in my garage, and one is synthetic, and the other is conventional. What about this stuff?

75W-90 is a different animal than 75W-85. There is conventional 75W-90 to be had but even most of the offerings in that grade have been either semi-synthetic or full synthetic blends.

It is not a cross I am going to die on, but from my search in the past, it is damn near impossible to find a commercially available 75W-85 grade gear oil that is a full conventional gear oil and labeled as such. There is some minor brands that will not even list whether they are conventional or synthetic but the assumption is they are synthetic based on the rest of the industry labeling that grade as such.

I dove into the issue of 75W-85 in years past when I had a FJ Cruiser as initially Toyota had the factory fill of a 80W-90 conventional gear oil grade in the early years. They eventually went to a 75W-85 not for fuel economy reasons but for better cold weather flow characteristic as they had problems in Northern USA and Canada winters differentials with the 80W-90 but the 75W-85 grade synthetic cured their issue. It was easier and cheaper to formulate a 75W-85 grade GL-5 spec gear oil from synthetic base stocks than to formulate from conventional base stock.

For purposes of the OP's question, it is safe to say the factory fill was a synthetic 75W-85 grade factory fill and probably a SOPUS product. Also, the MOPAR replacement 75W-85 grade gear oil sold at the dealership is a synthetic product.

So if people are wanting a white paper showing "all" 75W-85 sold on the market is synthetic, I do not have that, but the preponderance of the evidence of what is out there in 75W-85 grade gear oil shows it to be a synthetic product short of maybe an unknown unicorn product I have yet to see.

 

[oldhp3]

I just drained and refilled both diff's with FRAM synthetic 75W90 (Amalie OIL) from Car Quest. If you are pulling a trailer use 75W140 in the rear end.

 

[seven30]

Im putting this here for reference. The 540rat blog guy:
https://540ratblog.wordpress.com/
has a test setup for engine oils. He included a few gear oils and motorcycle tranny oils this year.

What I get from this is the same brand can have some of the best and worse products. So you cant go by brand, you have to go by a specific product and it could change over time, hence he retests periodically.

Here is a excerpt from his blog. Read the whole thing if want to understand how he tests.
----------
Here are the Engineering Test Data results of those 15 Gear Oils/Transmission Oils. The HIGHER the psi value, the BETTER the wear protection. They are ranked from the best # 1, to the worst # 15.


1. Amsoil 75W-140 Severe Gear, Extreme Pressure Synthetic Gear Lube intended for AUTOMOTIVE applications = 155,639 psi. Its actual viscosity/thickness is “somewhat thicker” than 20W50 motor oil.


2. Mobil 1 Synthetic ATF (automatic transmission fluid), Multi-Vehicle Formula, intended for AUTOMOTIVE applications = 129,447 psi. Its actual viscosity/thickness is about the same as 0W16 motor oil.


3. Valvoline 85W-140, GL-5 hypoid extreme pressure gear oil, intended for AUTOMOTIVE differentials = 128,221 psi. Its actual viscosity/thickness is “thicker” than 20W50 motor oil.


4. Valvoline 80W-90, GL-5 hypoid extreme pressure gear oil, intended for AUTOMOTIVE differentials = 122,187 psi. Its actual viscosity/thickness is the same as 15W45 motor oil.


5. Amsoil SAE 80 synthetic Dirt transmission fluid, intended for Dirt Bike MOTORCYCLE isolated transmissions = 118,239 psi. Its actual viscosity/thickness is the same as 5W30 motor oil.


6. Amsoil “Multi-Vehicle” OE ATF, synthetic, intended for AUTOMOTIVE applications = 113,677 psi. Its actual viscosity/thickness is about the same as 0W16 motor oil.


7. Amsoil “Fuel Efficient” OE ATF, synthetic, intended for AUTOMOTIVE applications = 110,531 psi. Its actual viscosity/thickness is about the same as 0W16 motor oil.


8. Pro Honda 80W/85 transmission oil, intended for Dirt Bike MOTORCYCLE/ATV isolated transmissions = 109,965 psi. Its actual viscosity/thickness is the same as 10W40 motor oil.


9. Motul 75W90 Gear 300 Synthetic Ester Transmission and Differential Fluid, intended for AUTOMOTIVE applications or Motorcycle applications where appropriate = 103,868 psi, API GL-4/GL-5, made in France. Its actual viscosity/thickness is the same as 10W40 motor oil.


10. Amsoil Manual Synchromesh Transmission Fluid, synthetic, intended for AUTOMOTIVE applications = 100,424 psi. Its actual viscosity/thickness is about the same as 5W20 motor oil.


11. Bel-Ray 80W85 Thumper Gear Saver Oil, intended for Dirt Bike MOTORCYCLE isolated transmissions = 99,848 psi. Its actual viscosity/thickness is the same as 10W40 motor oil.


12. Valvoline Synchromesh Manual Transmission Fluid, intended for AUTOMOTIVE applications = 95,220 psi. Its actual viscosity/thickness is about the same as 5W20 motor oil.


13. Motul 75W140 Gear Competition Synthetic Ester Transmission and Limited Slip Differential Fluid, intended for AUTOMOTIVE applications or Motorcycle applications where appropriate = 90,598 psi, API GL-5, made in France. Its actual viscosity/thickness is “somewhat thicker” than 20W50 motor oil.


14. Amsoil 75W90 Severe Gear Synthetic Gear Lube, intended for AUTOMOTIVE applications = 78,481 psi, for Manual Transmissions and Standard or Limited Slip Differentials that require MT-1, API GL-5 specifications. Its actual viscosity/thickness is the same as 10W40 motor oil.


15. Valvoline MAXLife, Multi-Vehicle ATF, synthetic, for High Mileage Vehicles, red bottle = 0 psi. Yes, 0 psi, that is NOT a typo. Its actual viscosity/thickness in this particular case, is even thinner than 0W16 motor oil. See the CONCLUSION section just below for the details on this ATF’s complete FAILURE.

 

[Mister Lamb]

Im putting this here for reference. The 540rat blog guy:
https://540ratblog.wordpress.com/
has a test setup for engine oils. He included a few gear oils and motorcycle tranny oils this year.

What I get from this is the same brand can have some of the best and worse products. So you cant go by brand, you have to go by a specific product and it could change over time, hence he retests periodically.

Here is a excerpt from his blog. Read the whole thing if want to understand how he tests.
----------
Here are the Engineering Test Data results of those 15 Gear Oils/Transmission Oils. The HIGHER the psi value, the BETTER the wear protection. They are ranked from the best # 1, to the worst # 15.


1. Amsoil 75W-140 Severe Gear, Extreme Pressure Synthetic Gear Lube intended for AUTOMOTIVE applications = 155,639 psi. Its actual viscosity/thickness is “somewhat thicker” than 20W50 motor oil.


2. Mobil 1 Synthetic ATF (automatic transmission fluid), Multi-Vehicle Formula, intended for AUTOMOTIVE applications = 129,447 psi. Its actual viscosity/thickness is about the same as 0W16 motor oil.


3. Valvoline 85W-140, GL-5 hypoid extreme pressure gear oil, intended for AUTOMOTIVE differentials = 128,221 psi. Its actual viscosity/thickness is “thicker” than 20W50 motor oil.


4. Valvoline 80W-90, GL-5 hypoid extreme pressure gear oil, intended for AUTOMOTIVE differentials = 122,187 psi. Its actual viscosity/thickness is the same as 15W45 motor oil.


5. Amsoil SAE 80 synthetic Dirt transmission fluid, intended for Dirt Bike MOTORCYCLE isolated transmissions = 118,239 psi. Its actual viscosity/thickness is the same as 5W30 motor oil.


6. Amsoil “Multi-Vehicle” OE ATF, synthetic, intended for AUTOMOTIVE applications = 113,677 psi. Its actual viscosity/thickness is about the same as 0W16 motor oil.


7. Amsoil “Fuel Efficient” OE ATF, synthetic, intended for AUTOMOTIVE applications = 110,531 psi. Its actual viscosity/thickness is about the same as 0W16 motor oil.


8. Pro Honda 80W/85 transmission oil, intended for Dirt Bike MOTORCYCLE/ATV isolated transmissions = 109,965 psi. Its actual viscosity/thickness is the same as 10W40 motor oil.


9. Motul 75W90 Gear 300 Synthetic Ester Transmission and Differential Fluid, intended for AUTOMOTIVE applications or Motorcycle applications where appropriate = 103,868 psi, API GL-4/GL-5, made in France. Its actual viscosity/thickness is the same as 10W40 motor oil.


10. Amsoil Manual Synchromesh Transmission Fluid, synthetic, intended for AUTOMOTIVE applications = 100,424 psi. Its actual viscosity/thickness is about the same as 5W20 motor oil.


11. Bel-Ray 80W85 Thumper Gear Saver Oil, intended for Dirt Bike MOTORCYCLE isolated transmissions = 99,848 psi. Its actual viscosity/thickness is the same as 10W40 motor oil.


12. Valvoline Synchromesh Manual Transmission Fluid, intended for AUTOMOTIVE applications = 95,220 psi. Its actual viscosity/thickness is about the same as 5W20 motor oil.


13. Motul 75W140 Gear Competition Synthetic Ester Transmission and Limited Slip Differential Fluid, intended for AUTOMOTIVE applications or Motorcycle applications where appropriate = 90,598 psi, API GL-5, made in France. Its actual viscosity/thickness is “somewhat thicker” than 20W50 motor oil.


14. Amsoil 75W90 Severe Gear Synthetic Gear Lube, intended for AUTOMOTIVE applications = 78,481 psi, for Manual Transmissions and Standard or Limited Slip Differentials that require MT-1, API GL-5 specifications. Its actual viscosity/thickness is the same as 10W40 motor oil.


15. Valvoline MAXLife, Multi-Vehicle ATF, synthetic, for High Mileage Vehicles, red bottle = 0 psi. Yes, 0 psi, that is NOT a typo. Its actual viscosity/thickness in this particular case, is even thinner than 0W16 motor oil. See the CONCLUSION section just below for the details on this ATF’s complete FAILURE.

Thanks for this. Amazing reference!

 

[Hootbro]

Keep in mind that 540 RAT does not publish exactly what his testing standards are and has side step any inquiry into his exact methods or if they follow any industry standard ASTM testing.

His gift of long winded writing and statement of "facts" without independent review of the actual raw data and where he contrives that info has appealed more to peoples confirmation bias if his stated "data" aligns with ones own.

Lubricants operate within a specified grade weight and viscosity range with motor oils, gear oils and even ATF having different specs for their respective viscosity that are not readily comparable to each other for a given viscosity with different demands for each type unique to themselves.

People like lists and rankings. 540 RAT appeals to that but I would not tie my hitch to his wagon on his ranking structure or methodology.

 

[WhyNotJeep]

I have a supply of Torco 85-140 RGL, non syn, GL6. It's what Currie uses in their diffs. Will probably be just fine when the time comes.

 

[seven30]

Keep in mind that 540 RAT does not publish exactly what his testing standards are and has side step any inquiry into his exact methods or if they follow any industry standard ASTM testing.

His gift of long winded writing and statement of "facts" without independent review of the actual raw data and where he contrives that info has appealed more to peoples confirmation bias if his stated "data" aligns with ones own.

Lubricants operate within a specified grade weight and viscosity range with motor oils, gear oils and even ATF having different specs for their respective viscosity that are not readily comparable to each other for a given viscosity with different demands for each type unique to themselves.

People like lists and rankings. 540 RAT appeals to that but I would not tie my hitch to his wagon on his ranking structure or methodology.

If you have a better source please share.

 

[ShadowsPapa]

It's interesting that all of the oils I've used over the last few years have ended up in or near the top of that list.............

Viscosities also don't indicate protection, so an oil that's 10w40 can be compared to an oil that's 5w20 for example, as far as protection.

But that's nothing to do with gear oil.
You can change to any "gear oil" - hypoid lube for differentials, synthetic or conventional, as long as it meets the specs. There's no fear or worry mixing or switching back and forth.

I've had issues with exactly one differential in my own personal vehicles over the decades and the one had over 150,000 miles on it when I got it. Bearings were toast but gears were perfect.
But seeing how these newer differentials are made, the efforts to cut friction and cut weight, the pinion bearings being ball bearings, they may be fine but it bothers me so these will likely get more attention than any other differentials I've ever had.

 

[seven30]

It's interesting that all of the oils I've used over the last few years have ended up in or near the top of that list.............

Viscosities also don't indicate protection, so an oil that's 10w40 can be compared to an oil that's 5w20 for example, as far as protection.

But that's nothing to do with gear oil.
You can change to any "gear oil" - hypoid lube for differentials, synthetic or conventional, as long as it meets the specs. There's no fear or worry mixing or switching back and forth.

I've had issues with exactly one differential in my own personal vehicles over the decades and the one had over 150,000 miles on it when I got it. Bearings were toast but gears were perfect.
But seeing how these newer differentials are made, the efforts to cut friction and cut weight, the pinion bearings being ball bearings, they may be fine but it bothers me so these will likely get more attention than any other differentials I've ever had.

Interesting as we have an F150 that suffered failed carrier bearings at about 110k. Its a V6 auto for heavens sake so perhaps some assembly error was responsible. I wonder about after market gears. Just about any set will last 35K or so but how many will come close to the OEM stuff.

 

[ShadowsPapa]

Interesting as we have an F150 that suffered failed carrier bearings at about 110k. Its a V6 auto for heavens sake so perhaps some assembly error was responsible. I wonder about after market gears. Just about any set will last 35K or so but how many will come close to the OEM stuff.

There's a heck of a lot of stress on carrier and pinion bearings. They not only turn but have to deal with the forces trying to move things in other directions. Under heavy torque, the pinion wants to climb the ring gear. That means there's a twisting force on the pinion - the end against the ring gear is trying to go up so the bearings have forces on them that wouldn't happen if those same bearing were in other locations. Similar for the carrier bearings. The carrier not only rotates, but it's being shoved around as well by those same forces. In my recollection over the years, and this could actually be explained by the forces acting on things during heavy acceleration, the right carrier bearing has been the worst or the first on those differentials I've repaired or rebuilt over the decades.
Hypoid gears have crazy forces working on them - they are a combination of gear types. More power is lost through hypoid gears than most other types. There's less friction once they are "Broken in" which is mostly a process of burnishing the surface of the gears by the rubbing action. And that's the key - they are like a worm gear in that there's a lot more sliding action than rolling action.
There's so much talk about these, the new Dana axles, being so strong and heavy duty and all that, but all of the cutting done to reduce weight, the reduction in bearing surfaces to reduce friction for better mpg and other factors, they would just seem to be not as heavy duty as used in some cars in the 70s and 80s - at least from the differential point of view. Axles, yeah, perhaps, depending on what you are comparing to, but the guts of the thing............. I'm not so sure.

 

[seven30]

My old 1965 Peugeot 403 had an actual worm gear axle. The ring gear was bronze. Letting off the gas of the 1500cc motor resulted in noticeable braking. And my little 250 Ducati had spiral bevel gear tower cam drive. This was early 70s. Neat stuff.

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