Are thicker gear oils better for differentials?

[Snagglefoot]

The Dino 80w90 is the recommendation from your 23 year old owners manual. Most Chevy modern manuals would recommend 75w90 Synthetic in the rear and some call for Dino in the front. I would go with 75w90 synthetic in both. Thickies love thick oil so do that if it rocks you. I have 260,000 miles on my Chevy 3/4 ton using AC Delco 75w90 Synthetic and a few other 75w90 synthetic store brand gear oils.

 

[Pablo]

First off, in my opinion, the SG 75w90 performed in the top two in SubieRubyRoo’s shootout, and I intend to buy some. ( Was just now checking out how to buy thru you). It was the video Buster linked to that said the new formula was not as stout as the older formula (I used the word “hollowed out” but that is what the video said in effect). Much less phosphorous, boron, and something else…also viscosity now less. But I’m pretty sure it was the newer formula the video was b**ching about that did so well in Subie’s shootout.

Thread 'Amsoil Severe Gear 75w-90'

Aug 23, 2024

Looks to be a mostly group III, with some PAO and ester.

Comparison to old formulation near the end.

• buster
• Replies: 9
• Forum: Gear, Transmission, Hydraulic oil analysis

• 
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Now, the one thing still holding me back is whether I should do the 75w90, which is already much thicker than Ford’s spec’d 75w85, or take your recommendation of the 75w110. Heh, I’ve even thought of mixing the 2.

I tend to believe Molakule. Follow his words closely.

Use the viscosity required tempered with your weather and load conditions.

Amsoil even makes a 75W85 for consideration.

 

[Impatient]

Here is the older (Antigua) SevereGear 75w-90 vs the newer (Nuevo) 75w-90 that the video was blasting. I understand the VOA’s don’t necessarily reflect effectiveness, as new non-tested components might make up for the lower phosphorous and Boron. I does make sense for Amsoil to target a lower viscosity to account for the realignment of the J306 grading.

 

[Pablo]

I actually don’t believe that. What date? Any confirmation?

PS All I am saying is I don’t trust the source or data. I am only working from my phone right now and tough to search but is there confirmation with a recent UOA?

 

[Impatient]

Let me do some damage control here, I am NOT trying to diss the Severe Gear product; like I said, I hope to purchase some soon. I am guilty of trying to absorb / react to several threads, and may have reacted in the wrong place in the wrong way…maybe.

1) I believe @MolaKule is saying the new formulation is not necessarily worse just because it has less phosphorus and Boron.

Many gear oils today are formulated with a Multi-Functional phosphorus package.

Amsoil is also using a base oil (a new group V) that has been used in wind turbine lubes to extend wind turbine transmission life.

I don't know what he said but lower phosphorus levels do not infer lower EP capabilities.

2) @SubieRubyRoo went to great length to do a comparison of ~12 different 75w-90 gear oils; he appears to have included the newer (“Nuevo”) lighter weight version, and although one could argue who came in #1 in that comparison, I don’t think anyone could argue Amsoil did worse than 3rd (same exact thing could be said about HPL, which had 2 different products in the test, if you catch my drift). One could argue Motul came in 4th, or 5th, but “the pack” was generally below that, jockeying for position, “trading this for that” or it was a price point argument. So among the 12 fluids, the Nuevo Amsoil 75w90 did pretty darn good.
3) I found a 2012 VOA of Severe gear and it largely matched the “Antigua” Amsoil VOA in the video. 2012! So, whenever it was that J306 was realigned, it shouldn’t be a surprise that Amsoil realigned its products to have a “lighter” 75w90 and a heavier 75w110. Buyers can choose which weight they want, and rest assured that both are quality products.

Now, where I have confused myself is which grade, which thickness, I should use. Should I try to stick close to Ford’s 75w85 recommendation, when they themselves have suggested their own 75w90 and 75w140 for the same axle in various similar vehicles? I hate to go too thick, sacrificing cold weather flow and fuel economy (to possibly to gain some protection in extreme conditions I may never experience) in my opinion 75w110 is the thickest I would consider, and frankly think the 75w90 is great enough.

 

[SubieRubyRoo]

Let me do some damage control here, I am NOT trying to diss the Severe Gear product; like I said, I hope to purchase some soon. I am guilty of trying to absorb / react to several threads, and may have reacted in the wrong place in the wrong way…maybe.

1) I believe @MolaKule is saying the new formulation is not necessarily worse just because it has less phosphorus and Boron.

2) @SubieRubyRoo went to great length to do a comparison of ~12 different 75w-90 gear oils; he appears to have included the newer (“Nuevo”) lighter weight version, and although one could argue who came in #1 in that comparison, I don’t think anyone could argue Amsoil did worse than 3rd (same exact thing could be said about HPL, which had 2 different products in the test, if you catch my drift). One could argue Motul came in 4th, or 5th, but “the pack” was generally below that, jockeying for position, “trading this for that” or it was a price point argument. So among the 12 fluids, the Nuevo Amsoil 75w90 did pretty darn good.
3) I found a 2012 VOA of Severe gear and it largely matched the “Antigua” Amsoil VOA in the video. 2012! So, whenever it was that J306 was realigned, it shouldn’t be a surprise that Amsoil realigned its products to have a “lighter” 75w90 and a heavier 75w110. Buyers can choose which weight they want, and rest assured that both are quality products.

Now, where I have confused myself is which grade, which thickness, I should use. Should I try to stick close to Ford’s 75w85 recommendation, when they themselves have suggested their own 75w90 and 75w140 for the same axle in various similar vehicles? I hate to go too thick, sacrificing cold weather flow and fuel economy (to possibly to gain some protection in extreme conditions I may never experience) in my opinion 75w110 is the thickest I would consider, and frankly think the 75w90 is great enough.

The 75w will control your cold weather flow. Brookfield # & CCS will also give you more information about an oil’s cold weather performance.

Ranking several of those oils is tough because based on very specific goals, the #1 choice would vary slightly. For me, I’d go by: lowest shear %, low 4-ball wear & high 4-ball weld, then price.

But the over-arching info that came out of all that testing to me was: pick a gear oil from a major, put it in and forget about it. It’s doubtful over the life of the average vehicle that any fluid choice from one of the Big 4 brands is going to significantly impact the life or operation. Gear 1 Plus on the other hand….

The closest thing we’ve got info on to your 75w85 is the HPL Diff Life Cold Climate 75w90. I’d use that and never bother wondering about anything else.

 

[MolaKule]

...I may never experience) in my opinion 75w110 is the thickest I would consider, and frankly think the 75w90 is great enough.

I use the 75W110 grade because it has 1) a thicker film strength than the 75W90 2) because it flows well in the cold temps up here, 3) it spans many of the older grades very well.

 

[meep]

I tend to stick with 80-90 or use the amsoil 110 weight. There’s another aspect which I don’t think was covered here, which is that the heavier weight gear lubes run hotter. If you’ve been towing heavy for a minute, you’ll have noticed that while transmissions have active cooling, rear ends do not, and they can get unbelievably hot when the gears are carrying high loads (towing). I wouldn’t use a 140 unless there was a defect I was covering.

 

[barryh]

I use the 75W110 grade because it has 1) a thicker film strength than the 75W90 2) because it flows well in the cold temps up here, 3) it spans many of the older grades very well.

A bit of a thread resurrection after a couple of months but what would be the effect of thicker diff oil on the oil temperature ?

We know thicker oil in a plain bearings will increase oil temperature but a diff is more boundary lubrication. I heard a report of thicker diff oil in a diff running cooler but that doesn't make sense to me unless the thinner oil was doing an inadequate job.

 

[IndyFan]

I’m getting ready to change my differential fluids (front and rear) on my 2001 Chevy Blazer 4door 4x4.

Right now I have Supertech 80w90 Dino gear oil in the front and rear diffs, which I put in about a year ago. There’s no noise from the differentials, so they are in good shape.

I just want to drain the diffs out and put some new fluid in, because last time I drained the diff fluids, the fluid had some metal in it, and it was black, from the previous owner.

Just trying to do some preventative maintenance, just to get the remaining metal out of the diffs!

So would thicker gear oils better protect my differentials?

I’m thinking of switching to synthetic 75w-110 from the recommended 75w90/80w90


Do thicker gear oils provide better diff protection, like thicker engine oils do in engines?

In the Jeep world, we have Dana Advantek axles (Dana 44). Jeep recommends 80w90 or 85w90 gear oil but 75w140 for towing or severe service on the rear only. But if you go to Dana, they recommend 75w140 across the board, front and rear.

That said, I ran 75w90 synthetic in my JK its whole life in the front diff and it never had an issue. Gears looked like new the last time I changed it at about 185k miles. In my JL Wrangler and JT Gladiator, I now run 75w140 at both ends, all the time, based on the Dana recommendation.

 

[oil pan 4]

A bit of a thread resurrection after a couple of months but what would be the effect of thicker diff oil on the oil temperature ?

We know thicker oil in a plain bearings will increase oil temperature but a diff is more boundary lubrication. I heard a report of thicker diff oil in a diff running cooler but that doesn't make sense to me unless the thinner oil was doing an inadequate job.

If someone changed their diff oil to a thicc one and it runs cooler that old could have 40,000 miles on it and be all sheared out and not providing good lubrication.
The dana rear end in my truck would likely be fine running ATF unless I was towing in the hottest days of summer.
The dana leaks so much I should be able to put a squirt of 75w-90 gear oil in the diff at every engine oci and be good to go never need to change it.

 

[MolaKule]

I’ll ask this again, since it pertains to the OP’s question.

What temps are considered normal in a standard rear diff? I know towing up a mountain pass in summer will be hotter than short tripping in dead of winter in flatlands, but what are some typical values, for say, 10 miles at 70 mph not towing, in 90F ambient? And at the towing scenario just mentioned? And 2 minutes into a drive starting from cold (say 32F ambient). Some YouTube vid I watched with a clear plastic rear cover showed super cold fluid providing little protection at first as it was flung off the gears and not circulating (whether that’s a real situation or not, I’m not sure, but the point of the video was that most wear occurs in the first few minutes of use, just like with an engine,).

Couple this info with the concept that thicker oil might run hotter AFTER it has fully warmed, sliding its viscosity toward the thinner end of its intended range. So one way to look at this is a 70w might be best for the first 2-3 minutes of any drive, then a little later on, a thicker 75w-90 fluid protects more, but then at extreme end (75w-140) MIGHT not have as clear of an advantage as the 100c viscosity rating might suggest, because maybe it is running at 100c, whereas a 75w-90 might be running at 80c under same conditions…and therefore not as thinned out as the “thicker” fluid. I imagine the 75w-140 might still have a protection edge, but not as great as the lab numbers might suggest.

Again, I mean this as a question, and maybe I’m off on the temp differences between fluids at high load. Maybe if our diffs had cooling systems which regulated the heat, or were heated-garage-kept in winter, the lab numbers (40c, and 100c) might be adequate in determining real-world performance.

Just thinking out loud.

Which is why, unless towing in the summer, I use 75W110 which provides the best of both worlds in terms of cold weather performance and sufficient oil film strength at elevated temperatures.

See post #27.