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Old 27-04-2020, 23:10   #1
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Location: Whaletown BC
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TwinDisc TMC-40 overfill... should I be afraid?

I realised with an inner Thud that a couple years ago I misidentified the gear on my Beta 25 (long story) as a TMC 60. It's actually a 40, as I realised last week after digging a little deeper. I don't have a really good excuse for making this mistake, so please don't ask

Anyway, for the last 400 engine hours or so I've been chugging around with about 3x as much ATF in the gear as it says in the spec. In the TwinDisc gear manual it does warn (in all caps, too) DO NOT OVERFILL. So I'm wondering what horrible things may have been happening inside the gear. It's been working perfectly, not a single problem, so I'm a bit puzzled.

There was a little leakage, but not much really. Could the seal have suffered? The gear is a mite rattly in operation, but it always has been (since before the first oil change where I made the mistake).

Anyway, when I extracted the old ATF it was definitely brown -- not black, not gooey, not full of metal, not emulsified, not weird-smelling, just brown. And it seemed to me it was almost the whole .6L, so there hasn't been a lot of leakage. I put in the right amount this time (shuffle, blush) ... though .2L seems like hardly anything at all... and am hoping I'll get away with having done something stupid.

Does anyone know what problems I should anticipate as a result, what to look for, etc?
Never too old to be messing about in boats...
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Old 28-04-2020, 00:37   #2
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Re: TwinDisc TMC-40 overfill... should I be afraid?

There's really nothing inside of it that would suffer if it was overfilled. Any excess pressure would be relieved by the breather. I reckon if it'll be fine.
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Old 28-04-2020, 08:25   #3
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Re: TwinDisc TMC-40 overfill... should I be afraid?

Never overfill small mechanical marine gears. If you do, the oil/ATF froths and frothy lube oil does not work very well for lubrication or cooling. It will also be pushed out the top vent. Fill the level to between the two marks on the dipstick.
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