Black gearbox oil
Discussion
Your thoughts please, gentlemen.
When I first bought my S2 it had a very crunchy reverse gear. When I checked the gearbox oil it was bright red and very thin. So presumably original special Ford oil or ATF. I had no reason to think it had ever been changed so as it was nearly 25 years old I sucked out as much as possible (slightly less than 1.5 litres if I remember correctly) and refilled with 75w90GL4. (Plate on the car shows GB oil as Century SS.80 which Google hasn’t heard of)
Gearchange was now perfect hot or cold, and as It never needed topping up I thought no more about it.
However checking the gearbox oil level this week I used a little tool I made out of white plastic which showed up that the oil was still very pink, (presumably from what remained of the original oil/ATF). So as I had a spare litre of Comma SX75w/90 GL4 I decided to use this to further dilute the remaining red stuff. I sucked out a litre and replaced it with the comma oil
When I crawled out from under the car and looked at what I sucked out I was horrified to see it was completely black. Under a lens it appeared to be full of tiny black particles. I checked with a magnet over the next couple of days and the particles do not appear to be magnetic so presumably non-ferrous, and neither did they show any sign of settling out.
So my question is, have I just disturbed 30 years of accumulated sludge which had been sitting harmlessly at the bottom of the gearbox with clean oil above it, or have I , by not removing all of the original oil caused something to precipitate out – such as lead sulphide. (it certainly looks like a precipitate as it is very evenly distributed in the oil).
And the next question is whether the particles are likely to be abrasive, and how much of the comma oil I need to buy to be sure of getting the inside of the gearbox clean, as I won’t be able to get all the oil out each time.
When I first bought my S2 it had a very crunchy reverse gear. When I checked the gearbox oil it was bright red and very thin. So presumably original special Ford oil or ATF. I had no reason to think it had ever been changed so as it was nearly 25 years old I sucked out as much as possible (slightly less than 1.5 litres if I remember correctly) and refilled with 75w90GL4. (Plate on the car shows GB oil as Century SS.80 which Google hasn’t heard of)
Gearchange was now perfect hot or cold, and as It never needed topping up I thought no more about it.
However checking the gearbox oil level this week I used a little tool I made out of white plastic which showed up that the oil was still very pink, (presumably from what remained of the original oil/ATF). So as I had a spare litre of Comma SX75w/90 GL4 I decided to use this to further dilute the remaining red stuff. I sucked out a litre and replaced it with the comma oil
When I crawled out from under the car and looked at what I sucked out I was horrified to see it was completely black. Under a lens it appeared to be full of tiny black particles. I checked with a magnet over the next couple of days and the particles do not appear to be magnetic so presumably non-ferrous, and neither did they show any sign of settling out.
So my question is, have I just disturbed 30 years of accumulated sludge which had been sitting harmlessly at the bottom of the gearbox with clean oil above it, or have I , by not removing all of the original oil caused something to precipitate out – such as lead sulphide. (it certainly looks like a precipitate as it is very evenly distributed in the oil).
And the next question is whether the particles are likely to be abrasive, and how much of the comma oil I need to buy to be sure of getting the inside of the gearbox clean, as I won’t be able to get all the oil out each time.
Edited by lewdon on Thursday 7th March 22:20
I am not familiar with the ford gearbox used on the S2, but is it possible to drain it out rather than suck it out?
Even if there is no drain plug is there a cover plate or side plate that can easily be removed?
If so, I would drain it out and then pour in a bit of new oil until you have clean new oil draining out.
If you have to remove a plate to achieve this, you can clean it as best as possible internally with a rag.
I am sure that years ago when I ran Scimitars, which I think had the same box, there was always a drain plug.
If there is no drain plug, and no convenient side or bottom plate to remove I would carry out very frequent oil changes until it is all clean when it comes out.
Even if there is no drain plug is there a cover plate or side plate that can easily be removed?
If so, I would drain it out and then pour in a bit of new oil until you have clean new oil draining out.
If you have to remove a plate to achieve this, you can clean it as best as possible internally with a rag.
I am sure that years ago when I ran Scimitars, which I think had the same box, there was always a drain plug.
If there is no drain plug, and no convenient side or bottom plate to remove I would carry out very frequent oil changes until it is all clean when it comes out.
Unfortunately there is no drain plug or other access,
It is theoretically possible to loosen the whole tail section of the gearbox, but i am reluctant to do this as I am worried that if the paper gasket tears it could create an oil leak which could only be repaired by completely removing and stripping the gearbox
It is theoretically possible to loosen the whole tail section of the gearbox, but i am reluctant to do this as I am worried that if the paper gasket tears it could create an oil leak which could only be repaired by completely removing and stripping the gearbox
No drain plug or side plate on a Type 9!
You can, very carefully, slacken the five bolts holding the tail housing to the main gearbox body and prize apart a millimetre or two (and hope the gasket doesn't split
). Majority of oil will drain out I've no idea what is going on with your oil but if particles aren't metallic I wouldn't think it's anything too serious
Think capacity is quoted as 1.9 litres, sounds like quite a bit of old oil may have been left in there?
I have been told that gearbox oil, unlike engine oil which is subject to fuel dilution and various products of combustion, just goes round and round doing what oil does and should "last forever"..... hence no drain plug.
"should last forever" - presumably except when it has bits in! 
I would have liked to find out what the "precipitate" is, and whether it is abrasive, as GB oil is so viscous, and it is so hard to get right to the bottom of the box, I suspect I am going to have to change it a lot of times to get it clean, probably running it in between.
There are also two grades of Comma 75w/90, SX (semi synthetic) and EP (presumably what used to be called hypoid). Any preferences?
Unless someone has advice to the contrary I plan to use SX.
I would have liked to find out what the "precipitate" is, and whether it is abrasive, as GB oil is so viscous, and it is so hard to get right to the bottom of the box, I suspect I am going to have to change it a lot of times to get it clean, probably running it in between.
There are also two grades of Comma 75w/90, SX (semi synthetic) and EP (presumably what used to be called hypoid). Any preferences?
Unless someone has advice to the contrary I plan to use SX.
Edited by lewdon on Friday 8th March 09:10
Edited by lewdon on Friday 8th March 09:49
Couple of links here for the type 9 box.
https://www.burtonpower.com/tuning-guides/tuning-g...
http://www.type9gearbox.co.uk/type-9-faults-and-pr...
Both state 1.9 ltrs to fill.
Good suggestion is to jack the front of the car as high as you can, remove the propshaft and drain the oil from the output shaft at the
rear of the gearbox.
https://www.burtonpower.com/tuning-guides/tuning-g...
http://www.type9gearbox.co.uk/type-9-faults-and-pr...
Both state 1.9 ltrs to fill.
Good suggestion is to jack the front of the car as high as you can, remove the propshaft and drain the oil from the output shaft at the
rear of the gearbox.
lewdon said:
Thanks for the links, much appreciated. But I would have thought the car would have to be almost vertical to drain the gearbox by removing the prop shaft. Unless I have misunderstood the layout of the box..
Your probably right, its just every time i removed the prop on the S3 that i once owned, the gearbox oil would start coming out.phillpot said:
I have been told that gearbox oil, unlike engine oil which is subject to fuel dilution and various products of combustion, just goes round and round doing what oil does and should "last forever"..... hence no drain plug.
Being constantly squished in between the teeth of the gears isn't great for it and over time it gets less good at doing its job, it only lasts "forever" in the sense that decent gear oil lasts as long as a typical ford sierra. 50000 miles/ten years or so is probably sensible, I change it whenever I have the gearbox out of a car.The only thing I can think of that you'd find in the oil in a gearbox that's black is molyslip but I'd not have thought that'd be especially particulate nor would I expect to find it in something that has a box designed for the use it's put to and a sensible oil in it.
The "black" is definitely tiny black particles suspended in the oil so I dont think it can be molyslip.
The fact that they are suspended evenly throughout the oil and not in clumps or blobs makes me think that it is a precipitate rather than just disturbed sludge from the bottom of the box.
So all I could think of is if the original oil or ATF used lead based additives, and the 75w/90 I added used sulphur based, they might have reacted together to precipitate Lead Sulphide.
If the precipitate is abrasive I will have to flush over and over again to get rid of every trace. If it is not then I only need to get rid of "nearly all" of it.
The fact that they are suspended evenly throughout the oil and not in clumps or blobs makes me think that it is a precipitate rather than just disturbed sludge from the bottom of the box.
So all I could think of is if the original oil or ATF used lead based additives, and the 75w/90 I added used sulphur based, they might have reacted together to precipitate Lead Sulphide.
If the precipitate is abrasive I will have to flush over and over again to get rid of every trace. If it is not then I only need to get rid of "nearly all" of it.
I would be inclined to agree with zombeh, above. Molyslip gearbox additive (this stuff:- https://www.ebay.co.uk/i/302534068078) which is good for easing crunching and whining 'boxes, is black and mixes entirely with the oil where it then remains in suspension..... This could very easily be the black 'particles' you see in your oil. Perhaps added by a former owner to ease the aforementioned crunch?
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