Repairing gearbox oil leakage

spirous · Jun 5, 2020

The gearbox is of "Simonet" make, driving a Schaublin/Simonet 102 hybrid, and i have noticed a quite slow pace leakage out of it. It leaks from both the two opposite sides as indicated in the pictures below. The leakage is quite slow, but in a couple of months, most of the oil has gone missing out of the gearbox.

Some of the screws holding the right mating plate (last image)have been found not been really tighten in place.
Around a quarter of turn was missing.
I' ve been thinking to make gaskets for the mating surfaces, in order to stop having leakage. the type of the screws been factory installed though, have simple slotted heads, not letting much torque to be applied, so i am wondering if the gaskets would be sufficiently pressed in place in order to seal...

I wonder if i should just try to tighten up the screws, refill with oil and wait and see what happens. Or if i should go with the gasket option. The thing is that i already took out the motor and that i would have to refit and wait another couple of months maybe to figure out if this did the fix or not.
On the other hand to fit gaskets would require even more disassembling, again with the possibility to fail, maybe even having misalignment introduced out of the (small) extra thickness..

Any thoughts/advise?

Garwood · Jun 5, 2020

John Deere cornhead grease is about $3 a tube. Won't leak anymore.

atomarc · Jun 5, 2020

I wouldn't use gaskets myself, rather I would find a good oil resistant gasket sealer like Loctite, Permatex or 3M Black, clean both surfaces well, install and let the gasket sealer dry. Many modern vehicles don't use traditional paper gaskets anymore, just ribbons of gasket sealer.

Stuart

pavt · Jun 5, 2020

I think a thin paper gasket would work especially if you also applied some silicone sealer.

steve-l · Jun 5, 2020

I cannot determine the source of your leaks from your photos. Only you can determine the source. Those deposits could be from the shaft seal(s) and simply weeping. If however the source of the leaks are the end plates, I would not use a gasket. Gaskets must be accounted for in the design, as they take space. If you have a metal to metal seam that is leaking, you should use a liquid gasket sealer like Threebond. This is not RTV. It is a case sealer typically used by Harley Davidson, Yamaha and many others to seal crank cases. If your leaks are at the shaft, there are other solutions like lip seals and oil slinger rings etc.

pavt · Jun 5, 2020

Garwood said:
John Deere cornhead grease is about $3 a tube. Won't leak anymore.

Yeah, but the OP is 5,000 miles away from the USA. I would be very surprised if cornhead grease is available to him.

spirous · Jun 5, 2020

thanks for the replies

the leaks are where the red arrows point to. Between the metal to metal mating surfaces and not out of the shafts.
I' m not aware of cornhead grease, but searching a bit for it, it looks like it is an additive to put in the gearbox with the oil and i wouldn't put anything else in the gearbox, rather than oil specified for this usage.
I have a couple of gasket making sealants around (one of it being permatex). This could be an option

Limy Sami · Jun 5, 2020

If it's driving the lathe - does the gearbox get warm / hot? ...if so check the breather's not blocked …...….or if it hasn't a breather - fit one.

pavt · Jun 5, 2020

spirous said:
thanks for the replies
.......
I have a couple of gasket making sealants around (one of it being permatex). This could be an option

The permatex is good, I've been using it for most of my life with no problems.

dian · Jun 6, 2020

pavt said:
Yeah, but the OP is 5,000 miles away from the USA. I would be very surprised if cornhead grease is available to him.

im sure john deere operates in greece, besides there are many nlgi 0/00/000 greases out there. but op wants to use "specified oil" only. why? is this running 24 hours a day? it would be the easiest solution for a leaking box.

spirous · Jun 6, 2020

John deere operates in Greece indeed. I don't use the lathe so much but it's a long story(the idea behind it being that it is a very old lathe (1930's or so) and different oil could affect it..), with a lot of research when buying the lathe about finding the specific type of oil recommended by the manufacturer.. I didn't think it was so important as well, but since i already got 20 liters of it, i am thinking of keeping it like so..
I' m leaning towards the gasket sealant option...

spirous · Jun 6, 2020

I' ve never actually noticed of the gearbox getting hot. And i was not aware of a breather function. But examining the bolt that i remove in order to put in oil, i see that it has hole peripherically. So i guess this would be the breather way and the holes look quite clean.

dian · Jun 6, 2020

yes, i know the problem with the oil, you have to buy ten times the amount you need. recently i began using hydraulic/way oil for cutting, no idea what to do with it otherwise.

pavt · Jun 6, 2020

Well, I stand corrected about John Deere operating in Greece. I am surprised by that -- I could understand Caterpillar being there, but I didn't think John Deere would.

In any case I think the grease is not correct, and the oil you have now is the right thing. Probably with the gasket sealer.

steve-l · Jun 6, 2020

spirous said:
thanks for the replies
the leaks are where the red arrows point to. Between the metal to metal mating surfaces and not out of the shafts.
I' m not aware of cornhead grease, but searching a bit for it, it looks like it is an additive to put in the gearbox with the oil and i wouldn't put anything else in the gearbox, rather than oil specified for this usage.
I have a couple of gasket making sealants around (one of it being permatex). This could be an option

DO NOT USE RTV!!!! RTV is a silicon sealant. Many gasket sealants are silicon based. Case sealants are PU based.

spirous · Jun 6, 2020

steve-l said:
DO NOT USE RTV!!!! RTV is a silicon sealant. Many gasket sealants are silicon based. Case sealants are PU based.

interesting comment. Actually i just noticed that the Permatex i have is old and will not do the job, but i have a versahelm "mega black", which suggested for use at transmission pans as well and it says that it is resistant to oil, but is referred as silicone gasket (it is this one http://www.itwconsumer.com/versachem-products/product.cfm?id=Mega%20Black%20Silicone%20O.E.M.%2C%203%20oz.-157)
So you suggest that this product wouldn't do the job and i should look for one that says it is PU based?

Limy Sami · Jun 6, 2020

pavt said:
Well, I stand corrected about John Deere operating in Greece. I am surprised by that -- I could understand Caterpillar being there, but I didn't think John Deere would.

In any case I think the grease is not correct, and the oil you have now is the right thing. Probably with the gasket sealer.

They also have running water and flush toilets.

Clive603 · Jun 6, 2020

Its clearly not made for a gasket so, assuming the case faces aren't abuse damaged, a sealer of some sort is the sensible options. Looks like there is a bearing in outer case so gaskets aren't best practice as they add clearance and reduce the stiffness of a joint when carrying loads side to side across the faces. Gasket joints are really for loads in line with the fixings.

I like thin non-hardening sealers like Wellseal for this sort of thing. Imperfections leading to leaks on faces made for metal to metal contact are invariably small. Stripped too many things where there are tiny traces of sealant in the actual joint and great gobs squeezed out round the inside. Hopefully still stuck to the casting but often spread around through the motor and oil filter!

Its difficult to get a thin enough layer of the thick sealants onto a joint not designed to contain the excess.

Wellseal is basically paint. Thin paint! After applying to the faces it is left to become tacky, 15 minutes or so. No squeeze out of the joint. Being non hardening it doesn't glue the joint together so it all comes apart cleanly if you ever need to get inside again.

Clive

spirous · Jun 6, 2020

Nice input Clive, thanks!
I become more persuaded that as excess thickness through a gasket could be a problem. There is a bearing in the outer case more likely as you said.
I like the solution of a thin, non hardening sealant. I don't remember seeing Welseal around, but i will do some local research for this or a similar product.

Limy Sami · Jun 6, 2020

Clive603 said:
Its clearly not made for a gasket so, assuming the case faces aren't abuse damaged, a sealer of some sort is the sensible options. Looks like there is a bearing in outer case so gaskets aren't best practice as they add clearance and reduce the stiffness of a joint when carrying loads side to side across the faces. Gasket joints are really for loads in line with the fixings.

I like thin non-hardening sealers like Welseal for this sort of thing. Imperfections leading to leaks on faces made for metal to metal contact are invariably small. Stripped too many things where there are tiny traces of sealant in the actual joint and great gobs squeezed out round the inside. Hopefully still stuck to the casting but often spread around through the motor and oil filter!

Its difficult to get a thin enough layer of the thick sealants onto a joint not designed to contain the excess.

Welseal is basically paint. Thin paint! After applying to the faces it is left to become tacky, 15 minutes or so. No squeeze out of the joint. Being non hardening it doesn't glue the joint together so it all comes apart cleanly if you ever need to get inside again.

Clive

I'm a big Welseal fan, sticks like the proverbial to a blanket and doesn't harden. FWIW the only thing I know that removes it is cellulose thinners.

FYI Stag Wellseal Jointing Compound 100ml Tube | Silmid

Repairing gearbox oil leakage

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