Why HTHS matters in your gearbox

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Blackstones comments are misleading.

Do any modern car manual transmissions still use 90W oil, mine uses MTF fluid that is 6.3 cSt at 100 deg C so not much different to ATF. Even the diff doesn't use 90W, it's 75W85.
 
Originally Posted by ZeeOSix
Originally Posted by BusyLittleShop
Quote Blackstone Labs on the Importance of Viscosity.

The oil's ability to act like a solid and protect parts is not related to its thickness.


The oil film thickness between parts certainly is dependant on the oil viscosity. It's that oil film thickness that keeps moving parts separated.

Blackstone needs to study up on tribology.


You can say that again!
 
Originally Posted by ZeeOSix
Originally Posted by BusyLittleShop
Quote Blackstone Labs on the Importance of Viscosity.

The oil's ability to act like a solid and protect parts is not related to its thickness.


The oil film thickness between parts certainly is dependant on the oil viscosity. It's that oil film thickness that keeps moving parts separated.

Blackstone needs to study up on tribology.


Yep, and epicyclic gear train versus a regular train, pich line speeds, tooth loading, gear length, how many gears share the load (planetary)...and viscosity.

AGMA have some pretty good resources on gear loads, viscosity and life...and viscosity is certainly a factor...
 
Originally Posted by Shannow
Originally Posted by ZeeOSix
Originally Posted by BusyLittleShop
Quote Blackstone Labs on the Importance of Viscosity.

The oil's ability to act like a solid and protect parts is not related to its thickness.


The oil film thickness between parts certainly is dependant on the oil viscosity. It's that oil film thickness that keeps moving parts separated.

Blackstone needs to study up on tribology.


Yep, and epicyclic gear train versus a regular train, pich line speeds, tooth loading, gear length, how many gears share the load (planetary)...and viscosity.

AGMA have some pretty good resources on gear loads, viscosity and life...and viscosity is certainly a factor...


Shannow,

For a bike's transmission, would you need separate EP/AW additives to protect it uniquely that you otherwise wouldn't have in an API SN Passenger car blend?
There is rare if ever a situation where it is appropriate to put a crankcase oil into a manual or automatic transmission, so how the exception/ build/ blend here with a shared sump?
 
Brian,
the EP gear oils use a different additive chemistry to engine oils...

Plenty of british cars shared engines and sumps, and plenty of others specced engine oil for separate gearboxes, and I did it in the '80s when proper GL4 was hard to find, and everything was GL4/5, and synchros baulked when cold.

If you had an SN, with a decent HTHS (say an A3/B4, with wet clutch compatibility, I doubt you'd ever have an issue....down here you can get relatively easily universal tractor fluids that are rated in just about everything.
 
Well, that's reassuring and helpful for you to mention all this.
Even those that run HDEO certed to VDS 4.5 should be getting a post-shear HTHS = or > 3.9
 
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