Yanmar 2GM20 gearbox lube

[Polarsailor]

I need to change the gear lube in my Yanmar 2GM20 gearbox. Looking at the dip stick it appears red like ATF fluid. According to the Manual it should have the same oil as the main engine, 20W 40. The gearbox is I think a KM2P. Larger Yanmar gearboxes I believe do use ATF fluid. Has anyone come across this before.

Not over keen on switching to 20W 40 as there would be residual ATF fluid in the gearbox even if I pump it out. The ATF fluid has been seems to have been fine and I haven't in fact changed it since I bought the boat a few years ago. Does anyone run this gearbox on ATF fluid and if so has it been fine?

Cheers Keiron

 

[RichardS]

My advice would be to use whatever is currently recommended by Yanmar, which might not be what is in the manual, so a call to their UK agent might be in order unless someone on here has the current advice.

Get as much ATF out as you can but don't worry some residual ATF, although you could always flush through once with engine oil if you are concerned.

I would not want to mix oil and ATF in something like an auto gearbox or power steering pump but in a manual gearbox it will not do any harm.

Richard

 

[JumbleDuck]

I would not want to mix oil and ATF in something like an auto gearbox or power steering pump but in a manual gearbox it will not do any harm.

Aren't these small Yanmar gearboxes more like auto than manual, with friction cones to engage gears?

 

[VicS]

I need to change the gear lube in my Yanmar 2GM20 gearbox. Looking at the dip stick it appears red like ATF fluid. According to the Manual it should have the same oil as the main engine, 20W 40. The gearbox is I think a KM2P. Larger Yanmar gearboxes I believe do use ATF fluid. Has anyone come across this before.

Not over keen on switching to 20W 40 as there would be residual ATF fluid in the gearbox even if I pump it out. The ATF fluid has been seems to have been fine and I haven't in fact changed it since I bought the boat a few years ago. Does anyone run this gearbox on ATF fluid and if so has it been fine?

Cheers Keiron

According to the workshop manual which you can find on line the oil for KM2 gearboxes is 10W30
(For KBW boxes its ATF )

However it would be wise as RichardS suggests to get the latest recommendations from your Yanmar agent.

 

[RichardS]

Aren't these small Yanmar gearboxes more like auto than manual, with friction cones to engage gears?

I was thinking more of a traditional auto gearbox with a torque converter where there's no frictional contact. However, it's the stresses on bearings and gears I was mostly thinking about. Car auto boxes are very precisely engineered because of the huge amount of power being transmitted to the high-friction tyres. Indeed, some of them like my current car, are sealed for life because of the problems if any foreign material gets into the box.

A residual amount of the previous lubricant in a cone clutch won't cause any problem if the the gearbox was working fine on 100% of the residual.

Richard

 

[JumbleDuck]

I was thinking more of a traditional auto gearbox with a torque converter where there's no frictional contact.

Traditional auto boxes do have frictional contact: the various gears are selected by applying band or cone brakes to stacked epicyclic gear systems within the gearbox. they are shown as "clutches" in this diagram:

 

[RichardS]

Traditional auto boxes do have frictional contact: the various gears are selected by applying band or cone brakes to stacked epicyclic gear systems within the gearbox. they are shown as "clutches" in this diagram:

Yes, of course they have loads of frictional contact ..... they're mechanical devices after all. However I'm talking about power transmission and that, unlike a conventional clutch, is not through friction. Whether this is relevant to the OP is another question entirely.

Richard

 

[JumbleDuck]

Yes, of course they have loads of frictional contact ..... they're mechanical devices after all. However I'm talking about power transmission and that, unlike a conventional clutch, is not through friction. Whether this is relevant to the OP is another question entirely.

There is no significant power transmission through friction in a conventional clutch. Except when it's in the process of engaging or disengaging, the power goes straight through. Precisely the same is true of the clutches in an automatic gearbox: the only difference is that they are internal and run in lubricant. The relevance here is that marine gearboxes also generally have lubricated clutches in them.

My Herald has a manual box with an epicyclic overdrive, so I get the best, or worst, of both worlds.

 

[RichardS]

There is no significant power transmission through friction in a conventional clutch. Except when it's in the process of engaging or disengaging, the power goes straight through..

You don't say!

You've presumably never stripped down a burned-to-a-crisp clutch plate?

Richard

 

[earlybird]

According to my "official" Yanmar GM workshop/service manual the KM2 and KM3 gearboxes, with cone clutches, ie GM10, 20 & 30 engines, use SAE10W-30 oil.
If that's correct, it's what the OP needs for his 2GM20.
The KBW10 gearbox, as fitted to the 3HM35 uses ATF. This gearbox has a multi-plate clutch.

 

[vyv_cox]

According to my "official" Yanmar GM workshop/service manual the KM2 and KM3 gearboxes, with cone clutches, ie GM10, 20 & 30 engines, use SAE10W-30 oil.
If that's correct, it's what the OP needs for his 2GM20.
The KBW10 gearbox, as fitted to the 3HM35 uses ATF. This gearbox has a multi-plate clutch.

My non-official manual says the same, in fact I believe it says to use the same oil as the engine takes.

 

[JumbleDuck]

You've presumably never stripped down a burned-to-a-crisp clutch plate?

I've never replaced a burned one, because I know not to burn 'em. I've changed a Citroen DS clutch single-handed, though!

 

[pagoda]

I've never replaced a burned one, because I know not to burn 'em. I've changed a Citroen DS clutch single-handed, though!

Snap! Though it was my son's Xsara. Not the easiest job to do. French engineering - for cars anyway, is not aimed at anybody except the first owner. And as they say "Hellmend the rest". I think they are better at yachts, since Japanese engines are regularly used

 

[thalassa]

My non-official manual says the same, in fact I believe it says to use the same oil as the engine takes.

That is what my manual says, also warns NOT to put ATF in. (KM gearbox).

 

[JumbleDuck]

Snap! Though it was my son's Xsara. Not the easiest job to do. French engineering - for cars anyway, is not aimed at anybody except the first owner.

To replace the clutch on a DS - an original Déesse, not the modern one made of cheese - you have to remove both front wings, the headlamp tilting and swivelling mechanisms, cooling air ducting, radiator, steering rack, suspension spheres, drive shafts, steering column, exhaust manifold and a few other bit which I have mercifully forgotten. It took me a full day just to have the engine fully exposed, a full day to get it out, a full day to change the clutch, and a full day to put everything back. That's it. If the new clutch wears out I'm buying a replacement car.

 

[pagoda]

To replace the clutch on a DS - an original Déesse, not the modern one made of cheese - you have to remove both front wings, the headlamp tilting and swivelling mechanisms, cooling air ducting, radiator, steering rack, suspension spheres, drive shafts, steering column, exhaust manifold and a few other bit which I have mercifully forgotten. It took me a full day just to have the engine fully exposed, a full day to get it out, a full day to change the clutch, and a full day to put everything back. That's it. If the new clutch wears out I'm buying a replacement car.

I bet the first owner never had that much bother

 

[Polarsailor]

Thanks all for your advice very appreciated.
Keiron

 

[ghostlymoron]

French engineering. On my Citroën GS, you had to remove the offside headlight to remove the first spark plug!
Re - yanmar, I'm pretty sure the handbook states same as engine oil for the gearbox. Mines a 2gm20FM indirect cooling.[ÀQUOTE=pagoda;5583006]I bet the first owner never had that much bother [/QUOTE]

 

[JumbleDuck]

French engineering. On my Citroën GS, you had to remove the offside headlight to remove the first spark plug!

A friend of mine had one of the old Peugeot 405 estates, and on that you had to remove the radiator to fit a fan belt. And let's not even think about cassette points in distributors ... <shudder>.

On the other hand, my Citroën 2CV was the best example of design for maintenance that I've ever come across. With one exception - setting the points gap requires removing the fan - everything on that car was easy to do because it had all been well thought out. They had 1939 - 1945 to refine the design, after all.

 

[rob2]

To replace the clutch on a DS - an original Déesse... If the new clutch wears out I'm buying a replacement car.

I guess the clutch has lasted quite well then?

I used to work in an automotive company where testing our product could mean extensive stripping of cars. All the test engineers were petrol heads straight from Uni and believed German cars to be brilliant and French carp. After a while working on them they came to agree that German cars didn't suffer electrical faults because they were all company owned (no-one could afford them) and French cars often had failed electrical accessories which never got fixed as you didn't use them anyway. Much the same with mechanics, but BMW are quieter inside - they have six inches more sound insulation.

Rob.