today's gear oil opinions

[Romer]

You've mentioned this a couple of times. Why do you think limited slip friction modifiers bad for ARBs?

Asking the question because it's something I've wondered, too. The friction modifier in LS gear oil is molybdenum disulfide. MoS2 is abrasive as a powder, although they use soluble MoS2 in gear oil so that might be the difference?

If this was a problem then wouldn't all the seals in LS diffs be leaking? I've never had a LSD to need the additive, so maybe they do leak faster? Maybe it causes engagement problems, e.g. friction preventing piston movement?

Taking this confusion point a bit further, they say not to use moly fortified (e.g. EP, extreme pressure) grease in wheel bearings because it can cause scuffing, but this seems like the opposite problem due to the high speed. They suggest moly in CV and slip yoke grease because it reduces friction.

FWIW, to Tim's original point it looks like neither of Lucas 75W90 synthetic and the 80W90 heavy duty conventional have friction modifiers in them.

ARB's site use to say about what gear oil to use in the locker
Any conventional or synthetic gear oil that is appropriate for your location and driving style. Stay away from anything that says “For Limit-Slip Diffs” or “Friction Modifiers”

There also was athread on Bob is the oil guy that helped me decide. The link to it I posted on mud doesnt work anymore

I had the Service manual and the BITOG thread in a post on Mud linked with that quote

Like I said in my first post, it has been 10 years since I did the research.

Looking at their current maintenance manual, it says there are no special requirements on lubricants. So that must have changed in the last 10 years.

Still lots to like about the Delvac. Saying what gear oil is the best is like saying what tire is the best. A lot comes down to rpefeerence

Likely any good gear oil is OK.

 

[C.Gerdo]

If it’s for a manual transmission, only use a GL4. I use Redline MT90 in my 2000 4runner 5 speed.

 

[Corbet]

Here’s a link to the product data sheet for Lucus 75w90 gear oil. Summit racing didn’t have much data and I simply wanted to confirm GL-5. Spoiler, it is. But if you want all the specs follow the link. I realized today the recommended service interval on my LC-250 is every 30K under severe conditions. And both Subarus need a service. So I’m also now overthinking all thing lubrication.

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www.lucasoil.com

 

[Corbet]

The 5 gallon bucket of Lucas 75W-90 was down to $122 at Summit Racing, I ordered that for the Subarus. My premium oil fetish won out and Amsoil 75W-85 is in route for the LC-250.

 

[Jacket]

GL-5 is the current shelf standard for most gear oil products from what I see. It's a lot harder to find the GL-4 when you need it.

 

[SteveH]

I just bought 2 gallons of this gear oil from Tractor Supply (shipped to store for free). $19.99/gal - 75w-90 synthetic, US-made.

https://www.tractorsupply.com/tsc/product/ultra1plus-sae-75w-90-synthetic-limited-slip-gear-oil-api-gl-5-1-gal-2438956

 

[Corbet]

Do I have a lubricant problem?