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Go Back   SailNet Community > On Board > Gear & Maintenance > Engines > Diesel
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Diesel This is a forum dedicated to diesel engines and their applicable accessories.


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Old 07-29-2014
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shifting issue with 3GMD/KM3-A

Looking for initial hints to troubleshoot the following shifting issue with my 3GMD and its typical Kanzaki transmission. Generally both the throttle and shift controls (1980's Morse single lever) work smoothly. However, on occasion, usually after motoring for a while, it will not shift from forward to neutral smoothly and requires a sharp hard tug to come out of gear. Once back in neutral, it will then shift forward and reverse normally again. Is this a symptom that others are familiar with? Not sure if it is more likely in the shifter/cables, or something inside the transmission/clutch.

I see no sign of operating issues like a slipping clutch, odd noises, etc. Whole motor/tranny has about 500 hours total use, over 29 years in a 6,000 pound catboat.

Thanks for all suggestions.
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Re: shifting issue with 3GMD/KM3-A

Is your transmission oil lvl good?
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Re: shifting issue with 3GMD/KM3-A

Good thought - I have not yet checked anything related to the shifting, and have not checked the tranny oil since launching. It has never lost any in the past, but could have done so.
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Re: shifting issue with 3GMD/KM3-A

Tranny oil doesn't go away suddenly (usually). That leaves the linkage, cables, or the lever on the outside of tranny. If it isn't there it is inside. If it was easy to remove the tranny fixing it would be no problem. It is a very simple piece of machinery.
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Re: shifting issue with 3GMD/KM3-A

I know that on Borg Warner types low oil will allow disks to run dry and stick. A failing pump (geroter on the main input shaft ) can also cause this.
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Re: shifting issue with 3GMD/KM3-A

The low oil feedback is great - just what I was hoping for, some ideas from others that have seen some similar issue. Hope it is that easy, but it does act just as I expect the dry disc's would feel (from Capt. Len). Once freed, works smoothly again. First thing I will check this weekend.
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Re: shifting issue with 3GMD/KM3-A

Just a quick follow-up, but my shifting problem may have just been dirty oil. It had plenty of oil when I checked this weekend, but it looked embarrassingly old - sort of milky cast to it as well. With fresh oil, it did hang up once, near beginning, and then seemed to be good the rest of the weekend, with couple of motoring legs that were long enough to have triggered the fault before. I will do another oil change next visit to be sure all of the old stuff is well gone.

Can anyone confirm the correct way to use the dipstick in the KM tranny? I believe you unscrew it , wipe, then re-insert it without screwing it down, to get the reading. If you need to screw it down, then the reading will be quite a bit higher on the stick. I have had various small gas engines with similar dip-sticks, and have seen that some manufacturers say to screw theirs down, others say to not screw it down.

Finally, what is the usual recommendation as to tranny oil changing frequency? (10-30 CC oil in this case).
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Re: shifting issue with 3GMD/KM3-A

Quote:
Originally Posted by mbsl98 View Post
Just a quick follow-up, but my shifting problem may have just been dirty oil. It had plenty of oil when I checked this weekend, but it looked embarrassingly old - sort of milky cast to it as well. With fresh oil, it did hang up once, near beginning, and then seemed to be good the rest of the weekend, with couple of motoring legs that were long enough to have triggered the fault before. I will do another oil change next visit to be sure all of the old stuff is well gone.

Can anyone confirm the correct way to use the dipstick in the KM tranny? I believe you unscrew it , wipe, then re-insert it without screwing it down, to get the reading. If you need to screw it down, then the reading will be quite a bit higher on the stick. I have had various small gas engines with similar dip-sticks, and have seen that some manufacturers say to screw theirs down, others say to not screw it down.

Finally, what is the usual recommendation as to tranny oil changing frequency? (10-30 CC oil in this case).
"Milky"? May indicate water is in there, mixing with the oil. It the transmission has an oil cooler, it may be leaking into the oil? If the oil level goes up that is likely. Perhaps you could have an oil analysis done, if it is water or coolant in the oil they could possibly identify it. Unless something bad is happening in the transmission the oil shouldn't be overly dirty, unlike diesel engine oil that turns dark/black fairly soon after changing.

Paul T
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Re: shifting issue with 3GMD/KM3-A

The old oil did definitely look like it was contaminated with moisture. It was not dark, but not what it should have looked like. It is a very basic Kanzaki with no external connections to any water source. Motor (simple 3GMD) is raw water cooled as well, so no apparent way for cooling water to get into the tranny that I can see. I hate to say it, but I have never changed that tranny oil in the 5 years I have had it (200 hours or so), so it may just be years of accumulated moisture? Once I change it again next week, I will keep a close eye on it to see how it "ages".
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Re: shifting issue with 3GMD/KM3-A

Quote:
Originally Posted by mbsl98 View Post
The old oil did definitely look like it was contaminated with moisture. It was not dark, but not what it should have looked like. It is a very basic Kanzaki with no external connections to any water source. Motor (simple 3GMD) is raw water cooled as well, so no apparent way for cooling water to get into the tranny that I can see. I hate to say it, but I have never changed that tranny oil in the 5 years I have had it (200 hours or so), so it may just be years of accumulated moisture? Once I change it again next week, I will keep a close eye on it to see how it "ages".
Boston, eh? From what I have read it gets cold there in the winter? "5 years"?
Very well could be some condensation has accumulated inside, mixing with the oil? If so, that is an easy fix, hopefully that is all it is. Perhaps the breather tube, if it has one, is blocked or crimped? Like all things mechanical, oil is their blood, & is cheap for what it does.

Best of luck with it.

Paul T
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