What oil filter

[liammonty]

The last thing you want on a Minor gearbox synchro baulk ring is extreme pressure oil. You need a oil that is quickly cleared from the baulk ring.
Everything else in the Minor gearbox can cope with EP oil.

That's interesting Phil as I understood that many other gearboxes that ARE specified EP oil use baulk ring syncromesh, such as the T2 VW I ran for years and also more modern vehicles. So presumably it isn't the actual principle of the way the baulk ring works that necessitates the use of engine oil in the Austin-derived Minor box?

I know that additives in some EP oils such as GL5 can damage the phosphor-bronze components in older gearboxes.

[philthehill]

All I can say in reply at the moment is that having tried engine oil and EP oil in a Minor gearbox the gear change was found to be better and smoother when filled with the engine oil.

[simmitc]

I agree with Phil. I purchased a car with EP90 in it and , although the oil was clean when drained, the box was far smoother when refilled with the correct engine oil. Every Morris and Castrol lubrication guide can't be wrong.

[kevin s]

Modern gear oils are nothing like the EP oils of the 60's the direction to use engine oil was probably the best there was 60 years ago but technology has moved on a bit since then.

At the end of the day it's much the same discussion as using radial tyres, alternators, electronic ignitions, disc brakes LED, bulbs etc, some will sway towards originality others taking advantage of the latest technology, there is no right or wrong.

[geoberni]

I've never stripped a Minor gearbox, but from what I've seen of people stripping them, they do have 'Yellow Metal' components, e.g. bronze, copper, brass or other such alloys.

There's plenty of info online, from professional sources rather than just forum gossip, which says that EP additives can damage such components, such as :

https://www.machinerylubrication.com/Re ... es-effects

As I see it, any owner can put in what they wish, it's their car, but it'd be pretty foolish to use any oil with lots of additives liable to damage the metals which are not found in modern gearboxes.
If someone really want's to switch from using 20W/50, they should at least use a gear oil that says it's for older designs....

There's as many Gear Oils out there these days as there are Engine Oils, modern designs seem to come up with newer specs for newer cars all the time.
The American market uses GL numbers, although the lowest of them are now deemed redundant.Certainly stay away from anything mentioning GL5....
Some specialist companies do still offer a wide range of GL numbers, e.g.
https://www.millersoils.fr/en/the-vario ... -etc-mean/

[kevin s]

The stuff I have been using is that meant for a Ford IB5, 75W90 Bo synthetic, As that trans was developed (as the B4)in the early 70's and contains bronze.
We had it in the original trans which sounded like bag of nails on engine oil, still sounded the same on the gear oil but didn't get any noisier over 3 years, I built a new one out of 4 old gearboxes and new bearings and that is nice and quiet, shifts nicely hot or cold and doesen't leak, If I'm still around in 30 years I'll probably be able to give you a more definitive answer on longevity!

I certainly wouldn't use a modern engine oil in gearbox , having seen how quickly things like Rover V8 cams wear without ZDDP. a classic oil should at least give something closer to what Morris specified.