Hypoid vs. Non-Hypoid

[Mark]

Can someone explain the difference between Hypoid and Non-Hypoid
oil? 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. What does Hypoid refer to and what is GL-5?
Thanks.

[Andy Dingley]

Mark <74551...@CompuServe.COM> 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 din...@codesmth.demon.co.uk

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.

[Richard Johnson]

Mark <74551...@CompuServe.COM> wrote:
>
>Can someone explain the difference between Hypoid and Non-Hypoid

>oil? 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. What does Hypoid refer to and what is GL-5?

Hypoid requires extreme pressure additives to the lube--will be labelled
as GL-5. These are normally sulfur compounds, which can break down under
extreme heat and attack yellow metals. Consequently, they should not be
used in applications which specify GL-4 only (or non-hypoid).
As an exception to this, AMSOIL synthetic 75W-90 or 80W-90 gear lube is
so formulated that it can be used in any application calling for GL-2
though GL-5.
AMSOIL also makes a synthetic 80W-90 GL-4 only.
Dick in Falls Church, VA
Using and selling AMSOIL over 17 years

[sophi...@gmail.com]

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 <74551...@CompuServe.COM> 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.
>