MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Transmission oil level

To all,
Can any one tell me how much oil I must add to move the oil level from low to full on the dip stick of a manual transmission with overdrive fitted to a 1970 MGB.
Also is it okay to use synthetic oil as a top up, I am not sure what oil is in there at the moment.
Thank you in advance of any advice.
David Levy

No idea, I just add bits till it shows Max. Usually engine oil of the same type as in the engine (although there is a factory document sculling around saying 80/90wt gear oil is acceptable), and I don't use modern high-spec low viscosity oils in either. Certainly nothing slippery with OD.
paulh4

I am not sure what oil is in there at the moment.
I wonder how many people stick to the service instructions, when it comes to gearbox oil on these cars, which is oil change every 24,000 miles or 24 months whichever is the sooner, not many I would think,
Andy Tilney

Unless you've already done so in the last two years why not take the opportunity to do a bi-annual/24k-mile oil change as per service schedule. Get the existing oil as warm as possibly for a thorough drain out for as long as possible to get as much existing oil and muck/crud out as possible.

As you carefully refill, allowing for the residue of oil that didn't drain, you could note the difference between low and full and let us know.

If you have O/D then you should also remove and clean the filter at the same time as the change.

With synthetic oils there are different types so I'd ask the oil blender as I'm sure if there is any doubt they'd say no and to use what the car manufacturer specifies.

I've seen it suggested to use a different oil (colour) in engine and gearbox to distinguish leaks.

There are loads of ideas, suggestions and beliefs as to which oils you should use in the car generally and this includes the gearbox - Millers Oils over here, on their website suggest their Classic Pistoneeze 30 (mono weight) but if you rang a technician might suggest alternatives.

Let us know how you get on.

Nigel Atkins

I didn't see Andy had posted whilst I was typing my reply - two great minds with the same thought. :)
Nigel Atkins

"use a different oil (colour) in engine and gearbox to distinguish leaks"

That's usually pretty easy, one is clean and the other dirty :o)
paulh4

Even as I was writing / posting the origional question I knew what I should do ie: change the oil. Please don't think I abuse my car I have had it for 15 years and in the early days when it was driven often as my second car in the family it received all the love and attention of a new bride.
How ever these days I have to make a special effort to make sure I drive it.
I drained 1800ml out of the gear box but could not remove the drain plug from the overdrive. Filled with 3750ml of non synthetic oil.
I had forgotten how much fun it is to get under these low cars and I am sure I will have aches and pains from jumping up and down during the process.
Job done and am enjoying a beer as I write this, thanks to all for your replys.
David Levy

David, you are a lot more enthusiastic about working on the car than me, often I have an ale instead, when I don't I wished I had.

1800ml doesn't sound like too much to get out on drain but 3750ml (unless it's a typo) sounds like a lot to get back in (but the relevant Driver's Handbook will give dry fill capacity).

After your first drive or test drive, once the oil has settled, it'd pay just to check it and top up if required then you know it's on the mark and next time you check you'll know if it's reduced.




Nigel Atkins

Nigel,
You are correct 3750ml should be 2750ml should have written the post before I started the beer.
if you can tell me how many ml's there are in a drip I can tell you how much I will lose buy counting all the drops on the floor of my garage, but I guess this doesn't count the drops I leave on the road when she is warmed up.
David Levy

David,
drips of oil are the car's way of constant oil flushing, a brilliant British idea that the Japanese failed to understand.
I would be a lot more concerned about wasted drips of beer, that must be stopped or reduced to an absolute minimum as soon as possible, personally I'm very strict about this.
Nigel Atkins

There is no drain 'plug' as such on the overdrive. The oil is shared between the two, and draining either drains the majority of it out of both. Once the gearbox has been drained it is usual to remove the sump from the OD in order to check the filter for lumps of friction material, and clean it, and that gets the remainder out.

The visible hex plug under the OD is for the relief valve assembly, but that does not drain the oil if removed with a full gearbox. Neither does removing the square cover-plate from the solenoid, i.e. both these can be serviced without draining the oil. It's normal to remove the relief valve assembly during an oil change to check and clean that as well, but be sure to note which way the valve plunger comes out of a working OD, as it can be refitted either way round, but disables the OD if incorrect. Also keep a clean container under the valve when removing it as sundry bits can fall out subsequently.
paulh4

Probably my bad memory again but I thought there was a drain plug on the earlier o/d but I also thought taking the filter out on the earlier o/d would drain it but in a more messy way - but I could well be wrong on one or both.

Certainly you'd want to clean the filter at each oil change and if there are problems look at and clean the valve pieces.

David has another thread about the o/d switch so perhaps if the problem is described it can be diagnosed or put on the path of diagnosis.

ETA: spoke too soon or rather too late, other thread is running diagnostics.
Nigel Atkins

1970 would have the later LH-OD.

Filter removal definitely drains the gearbox and OD - that's where the pumps sucks from - under the filter.
paulh4

Probably a daft question from a bloke who's had his car 35 years and over a 100K miles: on the '72 with the gearbox dipstick, when checking the oil level reading, presumably that's with the dipstick pushed back in, rather than just resting on top of the filler orifice?
Peter Allen

What's it say in the relevant Driver's Handbook?

As you don't want to overfill the gearbox without further information I'd go with dipstick pushed back in, as with the engine.
Nigel Atkins

This thread was discussed between 30/08/2019 and 03/09/2019

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.