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Hypoid vs. Non-Hypoid



 
 
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Old September 12th 17, 07:59 PM posted to rec.autos.tech
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Default Hypoid vs. Non-Hypoid

Thanks this was very helpful
Appreciate your time in posting.
Sophia

On Tuesday, 9 January 1996 03:00:00 UTC-5, Andy Dingley wrote:
> Mark > wrote:
>
> >Can someone explain the difference between Hypoid and Non-Hypoid
> >oil?

>
> "Hypoid" is not really a question of oil, so much as a question of
> gearcutting. Old (1920's) rear axles used straight bevel gears to form
> the crownwheel and pinion. These had two disadvantage, the pinion
> shaft meets the crownwheel on its central axis, and the straight cut
> gears are noisy. By using a more complex "hypoid" gear tooth shape (if
> you look at a pinion, the teeth appear twisted) these problems can be
> addressed. The more gradual engagement of the teeth along their length
> reduces noise. By careful design of the geometry the pinion can be
> made to mesh _below_ the axis of the crownwheel. As the centre height
> of the crownwheel is fixed by the wheel height, this allows the
> propshaft to be lowered relative to the car body, giving a clearer
> floorpan and lower centre of gravity for better cornering. Hypoid
> bevels are now universal in this application.
>
> Because of the sliding contact that hypoid gears make, their
> hydrodynamic contact pressure is higher. To be suitable for use with
> hypoid gears, a lubricant must be capable of resisting high pressures.
>
> Oils with "EP" ratings (Extreme Pressure) such as EP90 are required.
> Some brands describe themselves as "hypoid" instead, a term which is
> synonymous with EP. GL-5 is a formal API standard for this type of oil
> (comparable to MIL-L-2105B/C/D)
>
> > The book is telling me to use Non-Hypoid gear oil 80W or
> >80W/90 on the manual transmission and GL-5 hypoid gear oil 90W on
> >the rear axle.

>
> A manual transmission won't usually contain hypoid gears, so it
> doesn't need an EP oil. Rare exceptions are those transaxles where the
> crownwheel and gearbox share the same lubricant. Although an EP oil is
> more complex to manufacture, it has no disadvantages when used in
> instances where the EP attribute isn't strictly required. Manual
> steering boxes and other slow-moving oil-containing components are
> often filled with 90 weight oil. It's usual to buy EP90 because that's
> what the axle requires, then use the same oil for all other
> components.
>
> There's little practical difference between 80 & 90 weights. I fill
> everything with EP80 and I've never had a problem.
>
> There's an increasing trend amongst manufacturers to reduce the number
> of different lubricant types required. My own gearbox (5 speed Range
> Rover) runs on ATF, but 20W/50 engine oil or EP90 axle oil are equally
> permissible.
>
> --
> Andy Dingley
>
> The Internet has given us all mountains of information at our fingertips.
> ...and all most people want to do is pick their noses with them.


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