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Old 07-04-2007, 09:47   #1
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Unhappy Discolored Gear

My tranny started to slip on my Yanmar engine. It's a KBW10. The mechanic phoned last night and tells me the forward gear is discolored and looks like it was run without fluid. It's only got about 1400 hours and I have owned it since 700 hours. I never ran it without fluid and it does not leak and I know the previous guy was a stickler for keeping things up. Question, is a discolored gear trouble. Assuming no pitting etc should it be replaced? I can't believe it could get so hot as to discolor with fluid in there. The whole thing doesn't make sense to me.

Peter
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Old 07-04-2007, 14:33   #2
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Gears can be discolored by the heat treating process. If had gotten that hot, your tranny would have been smoke'n.

Slipage can cause heat but it should be the clutch plates that should be replaced. The oil would smell burnt and be dark.

What bothers me is the hours. 1400 is nothing. You should get 1000's. One would have to be shifting as if in rush hour traffic to put that much wear on a tranny. Are you bring the motor back to idle before shifting?

I think I'd be looking at the shaft on down and put in the proper tranny, reduce the prop and or pitch. And make sure the shaft is turning freely.

Some advice would be to take someone who has mechanical knowledge with and have them look at the gear as well as the rest of the parts and go from there.

Yours Aye!
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Old 07-04-2007, 19:30   #3
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It's a single handle control on the engine and we are generally careful when shifting. I went down and had a look at the tranny and gear and the plates are shot. I'm not sure why the gear is discolored but the gear looks OK to me. It's not wearing unusually or anything else. I have no idea why the plates are a goner. I bought the boat with 700 hours on the engine, hard to say what the history was. I'm finding it a bit of a challenge to provision a boat with a block holding an engine up in the campanion way.
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Old 08-04-2007, 01:17   #4
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When you say the gear is discoloured, what colour?? Blue is the sign of overheating and that wouldn't be possible with the power you have. I have seen gears on large trawl winches coming out of a bath of oil and then turning blue due the the enormouse loads, but that simply would not be possible in you situation.
Do you know why the plates have worn so early??? Did you have the correct oil? correct level?
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Old 08-04-2007, 07:48   #5
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You may want to check to assure that you are using the correct fluid in your transmission. Some of the Kanzai (sp?) transmissions used by Yanmar require HD30 oil rather than an ATF type fluid. Also check to assure that you have not been overfilling as these are "splash" transmissions that do not lubricate properly if overfilled.
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Old 08-04-2007, 08:11   #6
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Kanzaki Kokyukoki Marine Transmissions (or Hurth ZF) usually use standard SAE 20 or 30 engine oil.
Goto: KANZAKI

See also the previous thread “Tranny burning up” (Yanmar 2M20 with a Hurth KBW10 Transmission) at:
Tranny burning up (longish)


and

Hurth’s latest list of lubricants for Marine Transmissions
http://www01apps.zf.com/kst464/ZF_In...doID=1&id=1297
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Old 08-04-2007, 10:22   #7
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Thank you everyone for your replies. I've checked the olp requirements of this unit both from the service manual that came with the boat and from the stamp plate on the transmission. Both indicate an ATF type fluid and I have been using Dexron ATF. I had the boat out of the water last week, we have a MaxProp that I lubed and had checked by a mechanic. It changes direction properly with not drag anyplace. The shaft and cuttless all seem fine. When pulling the transmission out (in water) I could easily rotate and push the shaft in and out with my skinny arm extended way past it's normal range of motion. The gear in question is called the Forward Large Gear in the manual. It seems to have two parts, a larger slant set of teeth and a smaller spline gear where the friction plates ride. Only the spline is discolored, it is blue. The friction plates are badly worn and discolored as well. To the best of my knowledge the tranny has only seen ATF type fluid.
There is obviously something in it's history to suggest it was not always treated perfectly. I can imagine the plates getting hot enough to discolor but not the spline. There is just not that much contact from the plates to the spline. Given the small wear marks my guess it's less than a square mm per plate on each spline and there are 3 plates.
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Old 08-04-2007, 13:20   #8
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On another front, does the engine have to be re-alligned for the shaft coupling? Try as I may, I had to raise the engine in order to get at the tranny housing bolts. Will the engine re-allign properly onto the engine mounts? I have a drive saver between the couplings.

Thanks,

Peter
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Old 08-04-2007, 14:26   #9
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"Both indicate an ATF type fluid and I have been using Dexron ATF."
Dexron isn't the only type of ATF fluid, is it the correct one for your transmission?
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Old 08-04-2007, 14:37   #10
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HelloSailor,

That's a good question. The placard on the transmission calls for an ATF-A type of fluid. The manual indicates Dexron ATF, but of course is 20 years old and nothing is named the same anymore. The fluid I use is a Dexron III ATF, I will check into it further. It's all very confusing. A month ago I went into my Yanmar dealers and he tried to convince me that I should use 30SAE but I don't beleive this to be correct at all. It's tough getting the straight goods,

Peter
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Old 08-04-2007, 14:46   #11
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Peter-
I know Dexron-II and -III are both backwards compatible for Dexron applications but I'm not at all sure if Type-A is the same thing. IIRC last time I looked it up I couldn't find anything still in production that met the spec for Type-A but...I'm not at all sure of that. Someplace out there, someone still makes EVERYTHING for the antique car market, so Type-A must still be out there somewhere.

Put on your best poker face and ask your Yanmar dealer "So, if I use SAE30 instead of Type-A ATF, you'll give me a written warranty against lube failure in my transmission as long as I buy the oil from you?"

Watch him backpeddle, furiously.<G>
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Old 08-04-2007, 15:23   #12
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SAE 30 is for gear ONLY boxes. ATF is for Gear/friction plate boxes. Dexron ll and lll are for full auto transmissions, not usually found on boats. ATF should not be used where Dexron ll/lll are recomended. As Hellosailor states, it can be the reverse however. I think the vicosity is different between the ATF and ll/lll.
In saying all that though, the only way that gear could be turned blue in the box is for the box to have run out of oil. In which case, as stated above, the box would have been smoking. Besides, the splined shaft would also be blue.
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Old 08-04-2007, 16:38   #13
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Out of oil but not out of luck...

I've a Kanzaki transmision on my Ford. Heaven knows how it got there.

It's very stiff just before going into gear, but seems fine otherwise..

When I got round to checking it (after paying to have the fluid changed) there was no fluid in it, save for a few brown smudges at the bottom.

I filled it up with the ATF fluid that seemed most correct. I think I used the one for older cars.

I'd only run it for less than an hour though.

I wouldn't mind getting hold of a manual though, if it could be done cheaply.
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Old 08-04-2007, 18:38   #14
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Tranny oils

Another condition that can put stress on tranny's is motoring through a lot of kelp.

If I remember right the ATF type-A is now the Dextron II. The ATF type-F is now Mercon.

There are several types: Dexron II, Dexron III, Type F, Mercon, Mercon V, Chrysler 7176 and several varieties of Chrysler ATF-Plus. All are "friction-modified" lubricants except Type F. Dexron II and Mercon have similar additive packages as do Dexron III and Mercon V. Using the wrong type of ATF can cause transmission problems. If you do not know what type of fluid the transmission takes, it's best to find out.

The newer ATFs such as Dexron III and Mercon V are longer lived than earlier ATFs, but can still oxidize if the transmission runs too hot.

.............................................._/)
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Old 08-04-2007, 20:07   #15
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Guy's, you really have to try this stuff. It's very good. And no I have no affiliation with Amsoil in anyway shape or form. But I would if I could :-)
AMSOIL - Synthetic Universal Automatic Transmission Fluid
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