Hypoid or EP Gear Oil ?

It has taken me ages to find "Hypoid" gear oil as specified for the Transmission Oil for our Sillette drive leg. I finally came across this very old archived bit of the net with this definition.

"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)

So thats that resolved then - you can sleep easily now ! Thought I had better preserve this bit of the net 'cos is came from "74551.2327@CompuServe.COM" - somehow I doubt that email address still exists !