Morris Minor Owners Club

Hi, I'm a newbie on this site having just purchased a Minor 1000 and recently joined the Owners Club. I'm about to do a full service but I'm a bit confused about the correct oil to use in the gearbox and differential.

The Haynes manual suggests sae 30 in the gearbox but this site seems to recommend 20/50 so I'll go with that unless I'm mistaken. For the diff, the manual says to use EP SAE 90. I have just been sold Comma Gear oil EP80W-90 GL5 by my local motor factor but I'm not sure if this is correct. Any advise would be appreciated.

Very helpful site, I've already picked up a number of good tips. Nice to be on board

the comma diff oil you got will be fine in the diff,for the engine use 20/50 ,for the gearbox use 20/50 ,dont use ep 90.

The Series MM uses EP90 in the gearbox, the rest use engine oil.

As none of the others have said it - welcome to the Forum! If the gearbox is worn -then 20W50 will be fine - but if it'sgood - for best economy use 10W40. The engine however is best with 20W50 - doesn't need to be anything fancy - ASDA/Morrison stuff is fine. DO change the oil filter - and make sure the spring and plate are present inside the can - under the cartridge. For the winter - make sure the engine has anti-freeze in the cooling circuit! And make sure the air filter isn't choked solid with oil mess...............

Thanks for the advice and welcome

Hello PGH,

all the advice I've seen is not to use GL5 gear oil but GL4, the former does cause deterioration of brass\bronze components in the differential. Nothing wrong with the brand or grade just the type is not ideal.

Alec

I assume that this will not be a problem in the diff since, as far as I know, ther are no brass/bronze components. Please correct me if I'm wrong.

Hello PGH,

you may be right but generally the older differentials have bronze thrust washers for the sun\planet gears. Unless you can verify that there are none I would play safe and use GL4?

Alec

Mini has these (and runs on engine oil obviously) and they wear - badly! I don't think the Minor diff has them - but I don't have one handy!

All Minor diffs, from the Series II on, have (or originally had) bronze thrust washers for both sun and planet wheels - the same part numbers as the pre-A Plus Mini. There are replacement fibre ones, as used in the A-Plus Mini, but from the Midget forum, they don't have a very good reputation for longevity.

The early EP gear oils all ate into bronze type material, the standard GL5 EP oils just do it quicker, as they have a higher proportion of the 'extreme pressure' components that eat the yellow metal away. There do seem to be some 'yellow metal safe' GL4 and GL5 oils about, but without that clear label, the above advice about avoiding GL5 in a standard Minor diff looks to be very sound indeed!

All EP oils, unless specified as 'yellow metal safe', will still eat the bronze washers, as they have always done, just that as the spec has improved, so has the speed of 'eating'!

Gearboxes generally do not have EP oils recommended for them, to avoid the problems with bronze bushes and synchro rings. There are 'straight' 75, 80, 90 and occasionally 140 oils generally available for them, such as the semi-synthetic 75w/90 Castrol Syntrax that is used in the Toyota 5-spd box in our Minor.

Thanks for clearing that up Richard. After I wrote the earlier thread - I was thinking (while I was fence painting!) that it's the Minor diff that is in the Mini - and therefore indeed the Minor diff would have the bronze thrusts.

So, just for clarification, I do need an SAE 90 in the diff but not GL5. Is this correct.

Sorry for labouring this matter but as a newbie, I want to get it right.

Seemingly so!

Yes, the diff needs an 'extreme pressure' EP90 oil, ideally either a 'yellow metal safe' GL4 or GL5, but if it's not clearly labelled, then use the GL4 spec, not the GL5.

Thanks for the advice

hi i have i think the later rear diff with the filler plug the workshop manuel says 1.5 pints of ep 90 , but i have also read fill until oil comes out of the filler which would mean i would have to put in almost 3 pints to do that i am confused now as what s best any help would be great joe

They all have a 'filler plug' (I accept some non standard combos can end up with two, and some with none..) But I think 3 pints is far too much! Where are you seeing this 'filler plug' ??

hi thanks for your reply, i am seeing the fill plug half way up the diff if looking from the rear of the car also when driving the oil is leaking from the fill plug is that because its may be overfilled menu thanks joe

The plug should be just under half way up the back of the case and it doubles up as a level hole. You fill it there until it starts to run back out of the hole and that is the correct level. I don't know how much it holds though never measured it just tipped it in till it runs out

here is a photo of the. diff and filler plug regards joe