Morris Minor Owners Club

What's the best oil for a 948 gearbox? The book says engine oil SAE 30 / Castrol XL, just wondering whether an EP80/90 gear oil would be better?

Hard to see why it would be, or I think 'they' would have recommended it

Was just thinking along the lines that oils have developed alot over the past forty years and there may be something with better wear protection

I've never seen it recommended, sorry.

Just use the same 20W50 you use in the engine. EP90 is too thick and may cause problems with the synchromesh.

Do you use a modern 20W50 or one of the 'classic' branded oils?

I have been recommended to use MTF oil in my TR 7 gearbox - Manual Transmission Fluid - which I must say I have never heard of, but has supposedly been specially formulated for the job.! For the Minor box - just use whatever you are running in the engine, unless anyone has tried this MTF stuff and found it superior?

modern engine oils have been specially developed for extra life in an engine, but for a gearbox, a very basic 20/50 will probably be fine - e.g. SE or SF rating.
Using a moder 20/50 (SJ/SL/SK) rating would be a bit of a waste, as in the gearbox you don't need an oil that that's been developed to cope with the acids/carbon/extreme temperatures of an engine.

Is it ok to use a synthetic oil in the box?

I use the Halfords classic engine oil in both engine and gearbox then
Add some molly slip for gearboxes and molly slip for engines into the said applications. I know others add a ptfe additive.

Hope this helps

Additives in the gearbox will not help the syncromeshh - it needs friction to do it's work! In fact - I think they are a waste of money in both applications.
To-night I stripped a 1275 engine I acquired recently - never have I seen such a neglected engine - the water ways to the head were ALL almost totally choked with hard scale/debris - and the sump had the most foul smelling watery crud inside with really thick black sludge in the bottom!! Yet - the bores look fine, and when I pulled a big-end cap off the crank is PERFECT and the shell (std size) also looks absolutely perfect. So - it just goes to show how sturdy these engines are!!

Yep I agree bmc, they are sturdy but if its mine I like to keep it in as good a condition and health as possible and I think molly slip must help reduce wear and tear on moving parts so I put it in. Personal preferences.

The gearbox should have an engine oil, 20w/50 is ideal. All the EP oils have additives that 'eat' yellow metals, such as the bushes that the mainshaft gears run on. They are NOT recommended for the Minor gearbox and will wear it out much quicker.

As BMC said, the synchromesh NEEDS friction to work, less friction = less synchro efficiency, so 'friction' modifiers are not a good idea!!

I thought GL4 was "safe", it's GL5 spec that eats the bushes?

Yup, good old 20w/50 is best. I personally think you are better off with a modern version such as Duckhams or Castrol. The 'classic' oils are expensive and don't account for the fact that modern oils have moved on and are likely to be better as a result!

ASDA/Morrison 20W/50 is fine for engine and box.

Roy, When I used to work for a Mercedes benz dealership in Bradford MB used to specify ATF for use in the 207/307 (Transit size vans) gearboxes.

Given that the wise have pointed out that the synchromesh needs friction to work then whats wrong with adding the super sticky gearbox additive stiff - was going to try that in the steering rack neat when it gets changed as its real stuff to a blanket goo.
Used it before on a new noisy gearbox and the difference was immediate - way less noise, much smoother change etc.
Just thinking aloud as box oil is getting replaced soon.

Ian - have been advised I should change to ATF (or indeed MTF) for my TR7 gearbox (it's the excellent Rover LT77 5 speed unit) - but I dunno how that would do in a Minor box. Never had any bothers with engine oil in Minor box, so don't really see the need to change.

I've been down to my local motor factors and Comma seem to be doing a range of 'classic' oils with 5 litres of 20w50 / SAE30 or SAE40 at £12 which doesn't seem to bad to me.