Gear Oil

[Shasta]

Hello all,

I have done my due diligence and still am unsure on final drive gear oil.

Many of the oils suggested appear to contain a friction modifier (Mobile 1/Lucas etc...).

It looks like full synthetic 75w-90 is the most suggested but the ones I can find say LS so they have friction modifiers for limited slip diffs like my Jeep Quadradrive.

Thanks for any help and advice, Matt

[hubcapsc]

I've replaced the ring gear in several Valkyrie final drives. It's just a pile
of gears and bearings in there... I'd guess any quality goo that's Hypoid gear oil, SAE #80 would
be fine...

-Mike

[Willow]

The prohibition on friction modifiers is only for the engine oil that is used on the clutch.  There's no clutch in the final drive so friction modifiers should not be an issue.

[Ken aka Oil Burner]

As Willow said, you don't need friction modifiers in the final drive of the Valk, but they won't hurt a thing in there either. Use your preferred brand whether it has FM or not. No worries.

No friction modifiers in the engine oil though. It does matter in there.

[Robert]

Actually you do want friction modifiers in the final drive and you can use a heavier weight oil as long as its NOT a limited slip. Then it depends on the type of limited slip it is on weather you can change the oil spec.

Like some have said our bikes and most cars and trucks, all it is is gears no limited slip or anything like that.

I regularly use a 75/140 oil and liqui Moly additive in all of my rear ends on my vehicles regardless of what they call for.

Mobil 1™ Syn Gear Lube LS 75W-140

Liqui Moly 2019 MoS2 Anti-Friction Gear Lubricant - 50 Gram

https://www.amazon.com/Liqui-Moly-2019-Anti-Friction-Lubricant/dp/B00CPL8UPY

Heavier gear oil can translate to smoother vehicle and better gas mileage and longer lasting gears.

But DO NOT use modifiers in the engine oil, because of the clutch, like many have said.

[Chrisj CMA]

Hello all,

I have done my due diligence and still am unsure on final drive gear oil.

Many of the oils suggested appear to contain a friction modifier (Mobile 1/Lucas etc...).

It looks like full synthetic 75w-90 is the most suggested but the ones I can find say LS so they have friction modifiers for limited slip diffs like my Jeep Quadradrive.

Thanks for any help and advice, Matt

Two things

1.  Avoiding friction modifiers is for engine oil to protect the clutch

2.  You WANT friction modifiers in the rear end. Specifically GL5 or look for the words Hypoid Gear Oil. Don’t use it if doesn’t say either Hypoid or GL5 in the discription

[Chrisj CMA]

As Willow said, you don't need friction modifiers in the final drive of the Valk, but they won't hurt a thing in there either. Use your preferred brand whether it has FM or not. No worries.

No friction modifiers in the engine oil though. It does matter in there.

Hypoid gear oil has friction modifiers. You need hypoid gear oil. I recommend Lucas full synthetic hypoid gear oil. If it’s not hypoid yes there are worries

[Tundra]

Virgin olive oil

[Chrisj CMA]

Virgin olive oil

Lol. Ya as long as it’s EXTRA Virgin, probably just as good as non hypoid oil after a couple thousand miles of gear shearing.

[Ken aka Oil Burner]

Well, this went a bit sideways.

GL-4 and GL-5 gear oil is Hypoid gear oil. Hypoid gear oil contains EP additives, but it doesn't necessarily contain friction modifiers unless it was specifically added by the company that bottled it.

You can use a friction modifier if you choose, but it's not required or needed in the Valk final drive. There are no clutch packs in it. It is gears, bearings, and seals. Friction modifier was intended for automotive vehicles with a clutch-type limited slip differential. It helps to allow the clutches to be less "grabby" when wheel speeds are different. Without it, some vehicles will chatter around corners. None of this is applicable to the Valkyrie final drive unit. Some people believe that friction modifiers make the gear oil more "slippery", thereby reducing friction between gear surfaces. I don't necessarily feel that's true in the case of high pressure gear-to-gear contact. The EP additives in GL-4 and GL-5 gear lubes are engineered to provide the protection and lubrication for this type of surface friction. GL-5 has an additive package that is stronger that GL-4, and would be a better choice. Years ago, GL-5 contained activated sulphur that corroded yellow metals inside manual transmissions (bushings, synchros, etc). GL-4 did not, and it was the choice for manual transmissions. Since GL-5 no longer has activated sulphur, GL-4 use has dwindled, and now GL-5 is the most widely-used and easiest to find gear oil in the US.

So, as to the original question. You want a GL-5 rated hypoid gear lubricant. If it contains friction modifiers, that's fine. If it doesn't, that's also fine. In the service manual, Honda calls out "Hypoid gear oil, SAE #80". No additives needed. Finding straight 80 weight gear oil will leave you frustrated. Even Honda's own shaft drive gear oil is 80w90. 75w90 is fine, and you can find it anywhere.

[Chrisj CMA]

Ok, I thought the GL5 was a friction modifier. But still whatever GL5 is. We need it.

[98valk]

http://www.valkyrieforum.com/bbs/index.php/topic,110541.0.html    

How to select a good gear oil based on VI index.
« on: March 30, 2020, 11:41:52 AM »
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https://www.machinerylubrication.com/Read/28956/lubricant-viscosity-index

High or Low Viscosity Index needed?

If conditions are not constant (variable loads, variable speeds, variable ambient temperatures, etc.), then there is a need for not only the optimum viscosity but also a high viscosity index to stabilize the optimum viscosity. The more variable the conditions, the greater the need for high VI oils.

Also, keep in mind that for a great many machines there has been no past experimental or theoretical effort to identify the optimum viscosity. Viscosity selection is more of a wild guess. This too calls for a high VI lubricant.

A lubricant may merit having a high VI for one or more of the following reasons:

    The optimum viscosity is not known
    Varying loads and speeds exist
    Varying ambient temperatures exist
    To boost energy efficiency
    To boost oil service life (lower average temperature)
    To boost machine service life (fewer repairs and downtime)

Cheaper, lower VI lubricants may make sense if:

    Speeds and loads are constant
    Temperature is constant (constant ambient temperature or a heat exchanger is in use)
    The optimum viscosity at the operating temperature is known and is consistently achieved

For 75w90 oils;

checking mobil 1 gear oil, it actually has a low VI and according to the above is not good for valkyrie final drives which needs a high VI.

Mobil 1 syn gear oil has a VI of 146.
https://www.mobil.com/en/lubricants/for-personal-vehicles/our-products/products/mobil-1-syn-gear-lube-ls-75w-90/

checking some others, Valvoline syn has a VI of 150.
https://sharena21.springcm.com/Public/Document/18452/3e467451-fe75-e711-9c10-ac162d889bd3/cf662252-0bbd-e711-9c12-ac162d889bd1

Valvoline high performance gear oil 75w90

VI 166
40cst  99
100cst 15.9
pour point C  -39 degrees

Peak Auto syn has VI of 162  and has the lowest cost.
https://peakauto.com/wp-content/uploads/2017/01/PEAK_Gear_Lubricant_Oil_75W90_75W-140_Oil_Spec_Sheet_2016.pdf

Amsoil severe gear has VI of 166.
https://amsoilcontent.com/ams/lit/databulletins/g2043.pdf

Amsoil long life has VI of  143.
https://amsoilcontent.com/ams/lit/databulletins/g2042.pdf
This is what I've been using for years in my vehicles.  I'll be changing over to Peak from now on.

interesting that the article considers a Low VI as cheap oil.

[Shasta]

Thanks everyone.