# yanmar 2gm km2a tran



## joannemary (Mar 20, 2008)

tran is slipping on full throttle can any body help is it oil and is it hydrolic oil


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## PBzeer (Nov 11, 2002)

The trans on my 2GM uses 30w non-detergent oil. Have you checked the level in your trans? When was it last changed?


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## joannemary (Mar 20, 2008)

*2gmtran*

just bought boat oil change not known but is it a hydrolic box?


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## JohnRPollard (Mar 26, 2007)

In most sailboat installations I'm familiar with, the 2GM was coupled with a transmission that used the same oil as the engine.

Here's a helpful resource: Link


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## PBzeer (Nov 11, 2002)

No, it is not hydraulic oil.


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## joannemary (Mar 20, 2008)

*2gm tran*

is it a cone box


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## querencia (Oct 7, 2000)

*2GM Transmission*

I think that you are going to find that the cone is slipping and 
needs to be replaced,When mine was going, I was able to hold the shift lever all the way forward while bringing the engine speed up slowly [ Assuming you have two separate levers ] and that seemed to solve the problem on a temporary basis until the wear of the cone got worse and the only solution was a repair, Yes, the transmission uses 30W oil just like the engine,it holds at the most maybe 8 ounces !!!
Ed


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## joannemary (Mar 20, 2008)

will the oil level cause problem. thanks for the info


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## PBzeer (Nov 11, 2002)

Yes, improper oil level can be a problem.


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## Northeaster (Jan 13, 2007)

There was a post, in Yanmarhelp.com, or Torresen Marine's forum, where a guys described how to take the trannie apart, and lap the cones with valve lapping (gritty) compound, so that the drive cones will catch better against the forward / reverse gears. I have read that it is a common problem, that they become glazed / slippery, and won't engage well. Some have said it should be done every few years.

Related question, I have exactly the same setup, and have read that normal engine oil is used in the trannie. Before I read this, however, I read in my yanmar manuel, to use a Dextron 3 type fluid, so I topped up with this type of fluid in there, for the last 20 hours of so, last year. Seemed to work the same.

Taking the trannie apart now, to lap the cones / inspect things.
Just wondering if I should put engine oil in next year, or Dextron 3 type.


Thoughts?


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## PBzeer (Nov 11, 2002)

If you check the LINK in post #4, you'll find a listing of the various transmissions and the proper fluid to use. I would assume though, that if you have the proper manual, then you should use what it recommends.


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## billangiep (Dec 10, 2003)

Lapping the cone would make matters worse, increasing the slippage. What you can do is take the cone out and reverse it but this would likely give you the same problem only in reverse gear. 
When shifted into gear the cone slides down the shaft and is seated into a female type socket. It is held there with an external spring attached to the end of your shift cable and then to the shift arm of the trans. The spring is a barrel looking thing that loads both in reverse and forward. Nine times out of ten the spring is froze inside the barrel causing premature cone wear.
The newer multi-grade oils are just to slick. Although they may be good for your engine they are not so for the tranny. As PB suggested use non detergent 30w for the 2gm (7 oz.) and 3gmd (11 oz.) To check the fluid level do not screw in the dipstick rather just rest it on the top thread. If you roughen up the end of the dipstick and spray with some flat black paint it helps in seeing the oil level.


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## Northeaster (Jan 13, 2007)

Billangiep -

I haven't taken my trannie apart yet. But, I was under the impression that the mating surfaces of the drive cone and respective forward, and reverse, gears can become glazed, so they slipp. I have read, and would think it logical, that using a valve lapping compound, while "grinding" the cone into the gear, would rough up the surface, and make it less slippery.

Just trying to learn / understand how it works - Can you explain, a bit more in-depth, why lapping would not work, and maybe offer other suggestions.
I have rad accounts of several people, who have used this method, and were happy with the resluts.

Thanks!!


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## billangiep (Dec 10, 2003)

North, The difference between a worn out cone and a good one is only a few thousands of an inch.The cone is made of bronze and much softer than it's female mating surface. By lapping you would remove even more of the cone. Another words after lapping and reasembling...you shift into forward gear and the cone will never reach it's female matting surface. 
If your going through the trouble of removal and disassembling I think it would best to replace the cone, the tail shaft bearing and associated seals at a min. Your probably looking at around $250.00 . I'm not a mechanic by trade but have had much experience with the 2 & 3 gm's tranny's and %100 of the time the cone's were worn due to improper adjustment of the shift linkage. 
Bill,

P.S. If your not familiar with what a cone looks like I have a couple in the work shop I'd be more than happy to snap a photo?


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## Northeaster (Jan 13, 2007)

Billang - Thanks for the info. My trannie actually worked fine, although I had a problem with a Mickey mouse shift lever. I needed to take the 4 bolts out, that hold the shift lever on the side. The previous owner had it set up to shift front to back, instead of the original 12 o'clock to 3 o'clock movement. They did this, as the yreused the old controls, and set up the shift cable to work form a bracket behind the trannie, instead of the bell housing mounted bracket. I will be changing back to the original bracket, and changing the lever movement accordingly.


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## Northeaster (Jan 13, 2007)

Billang - Since I have it out of the boat anyway, I thought I would have a look at the cones, wear in general, to make sure it's good for a few years. My brother is a mechanic (auto), and is working on it for me. 

I have only seen the Yanmar drawings of the parts. Would be great to see pics of good vs worn cones, to have an idea of what is acceptable.

Thanks for the info!!


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## billangiep (Dec 10, 2003)

These are both used cones, the one on the left is from a 3GMD with a bad reverse gear and the right one is out of a 2GM with a bad forward gear. The shift fork rides in the center trowing the cone down the shaft. Centrifugal force will hold it there during higher rev's but it is dependent on that barrel type spring attached to the end of your shift cable to hold it during the lower rev's. It is ever so important that this is adjusted correctly putting proper tension on the shift arm both in forward and reverse. This has been my experience on GM model's prier to 1987 and in later years, not sure when, but they went with an internal tensioner.
Visually it is difficult to tell what side of the cone is bad, here's a look at $500.00 worth of paper weights.

















additional photo's
billangiep/Tach - Photobucket - Video and Image Hosting


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## Northeaster (Jan 13, 2007)

Billang- thanks for taking the time, to post the photos. 

As mentioned, my trannie worked well (ie Did not slip out of gear once engaged). However, with my previously descibed PO Mickey-moused shift cable, I did have alot of trouble getting it into both fwd and rev gears. I tried adjsuting the cable throw numerous times, a bit closer to fwd, rev, etc. 

Once I started reading more / asking questions, I found out that I was missing the spring joint device, on the end of the shift cable. The PO just used a clevis pin, at the end of the cable. 
When I would shift the pedestal lever into gear, I would usually have to run below, and manually push the trannie lever a bit more, to go into gear. Then it was fine, unless I idled very low, I would have to do it again. Definitely plan on fixing that this year.

Have bought a new normal / thin Morse cable, the spring joint, and will be repositioning the trannie lever back to it's stock position. I have a knock-off edson pedestal (Yacht Specialties, 1978) iwth separate controls for shifting and throttle. Last year it had the original "thicker" shift cable.

Any advice / thoughts you would have on this would be appreciated.


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## billangiep (Dec 10, 2003)




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## Northeaster (Jan 13, 2007)

Billang - (or anyone!!!!)
Thanks for posting the shift diagram. I don't have my Yanmar book on me, right now! 

As mentioned I need to change my lever throw position (from the current bast$rdized approx. 10' o'clock to 2 o'clock position, to the original position (shown in your diagram).

I had thought I would need to take out the 4 bolts, in the cover ,to move it.

Looking at the diagram, it looks as if I can just loosed the 1 small bolt, holding the lever to the shaft, to change the lever position, correct???

You mentioned adjusting the lever / cone movement, with just 1 bolt!! Is that the bolt shown in the bottom of the diagram???

The engine is currently a 4 hour drive away, so I woudl like to have a good idea of what needs to be done, before working on it again!! 

Thanks for the help!!!


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## billangiep (Dec 10, 2003)

North you don't have to remove the cover plate. Loosen the one bolt on the shift arm and you can rotate as needed. I believe the lower plug on the case holds a spring and ball (detent) for F N R. Once you have the shift arm correctly orientated (90 degrees from the cable to the shift arm while in neutral) the adjustments are made with the shift cable and spring joint.
Bill,


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## Northeaster (Jan 13, 2007)

Billang - Thanks again for all of the help. 
So, just so I am clear. I know that my throttle cable needs to have a tension clamp on it (did this last year), as the rpms would reduce otherwise. But, are you sure that the shift cable needs this type of clamp as well, in addition to the spring joint cable connector? Last year, I didn't have either a tension clamp, or a spring joint, on the shift cable - and obviously, it didn't work well!!


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## Northeaster (Jan 13, 2007)

Billang - Finally found that old thread on Yanmarhelp.com, where it was recommended to lap the mating surface of the drive gear - which the cone slipps against - I referred to it as lapping the cone itself.

Just thought I would provide the source of the info!

Quote!!!
Had similar problem with 2GM 15 several times.
The inner face of the gear that the bronze clutch cone spins into has become glazed, resulting in slippage when put into gear. Cone will heat up because of slippage give a few clunks the engage. Solution is to dissamble gear box, apply a bit of valve lapping compound to inner face of the gear, lap the cone into the face for about a minute, clean everything carefully and reassemble.
There is an adjustment on the shift lever houseing that must be made to ensure equal travel in foreward and reverse, this is critical to avoid reaccurance of problem.

and ..

The cone does not wear, the race that it spins into gets glazed from slippage and prevents proper mating of the two faces. while this slipping is occuring the cone heats up and expands, you get the clunking sounds then away you go.
The spring joint insures that a positive pressure is always on the shift lever, if there isn't, slippage can occur from cable creep.

End quote!

Full thread available at link:
Yanmarhelp.com Message Forum - Yanmar marine diesel engine help & advice -> 2GM20 Forward Gear Problem


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## bernard50 (Dec 10, 2003)

Hey Guys,
Can anyone help me,....I had my cone drive in my KM2A lapped and have used it for 30 hours. It now again is causing the entire engine to shudder ONLY in forward gear,...only at operating temp,...and only between around 900rpm to 1800 rpm. The engine oil may well be something to consider...but why does it not happen in reverse??
Any help would be much appreciated.
Bernard


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## r.furborough (May 28, 2006)

bernard50 et. al. 

You are suffering from a maladjusted shift mechanism/cable. The KM2/KM3 and the down angle 'a' variants are very sensitive to this and possibly a weak detent spring on the shift mechanism itself. I do not discount a worn cone clutch, but the shudder/banging of the transmission is a classic sign of this.


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## Northeaster (Jan 13, 2007)

Does it do it when you manually shift the lever on the transmission? (instead of shifting the lever in the cockpit). 

For those who have read all of this thread. I (and my auto mechanic brother) took my 25 year old K2Mp transmission off of my Yanmar 2GM last winter. Took it apart, lapped the cones, and replaced reconfigured the shifting lever wit hthe proper Yanmar parts, and Morse cable. 

I have had zero problems last season or this season and am extremely happy with the results.
Thanks to all those who gave advice!!


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## jeffls (Mar 5, 2008)

I have a spare kanzkai km2a transimission. I am posting it on ebay but if I don't get any interest I'll be putting it back in storage. If you still need one send me a pm.


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## garneauweld (9 mo ago)

jeffls said:


> I have a spare kanzkai km2a transimission. I am posting it on ebay but if I don't get any interest I'll be putting it back in storage. If you still need one send me a pm.


Silly question - Still have the km2a? Thank you, Garneau Weld


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