Need advice on transmission problem, please

[Frank Langer]

Hi,

I would really appreciate some advice on how to proceed with my transmission. I have a Twin Disc MG340 which was installed new last summer after my original Hurth 50 transmission died. The new one has been working fine, with about 100 engine hours since it's installation.

However, my last sail was in very windy/wavy conditions and the transmission slipped about 5 times during a three hour trip home motorsailing. It would be fine, then without warning the engine would rev much higher and I could hear a sound like when shifting badly in a manual drive car. I immediately shifted to neutral each time, leave it there for a moment and then shift to forward and everything was fine til it happened again. It has never behaved like this before.

Back at the dock I found the fluid level to be normal, but the normally quite pink/red fluid looked purple like a good red wine. It did not smell burnt, and still felt normal. I drained the fluid, didn't see any metal flakes in the drain pan and refilled it with new fluid. I then ran the engine in forward gear for about 20 minutes while tied to the dock and it sounded normal and didn't slip at all.

Last thing, I checked the shift cable linkage to see if anything was loose, but it was all tight (cables replaced last year). However, I noticed that when I shifted into forward gear at the pedestal to it's normal forward position, when I went below to the transmission I could push the shift lever on the transmission another 1/8 inch or so forward which seemed to lock it more solidly into position. This last push moved the gear shift lever at the pedestal to it's maximum forward position.

In short, I think I may have been a bit hesitant to push the gear shift lever far enough forward, as my last cable had gotten kinked because I think it had been bent too far in shifting. So instead of recreating that problem, I would shift into gear until I could feel the transmission engaging and the boat moving forward--made sense to me and worked fine til this last time.

So my current diagnosis is that I had not been shifting the gear shift lever far enough forward to lock it into gear effectively, and in the wavy conditions of my last sail (3 foot plus choppy waves), the motion of the boat may have been enough to dislodge the gear shift lever enough to have it slip partially out of gear.

So now my question. I am contemplating changing the fluid one more time to ensure that all the old fluid is gone and then watching it carefully for the next few weeks to see if the problem reoccurs; hopefully my diagnosis and remedy are accurate and I'll be ok. I am a bit concerned that I may have done some damage, as it didn't sound good when it slipped and the dark purple fluid is not a good sign. Is there any way short of taking the transmission apart to tell if it's ok or been damaged?

Finally, the transmission is still under it's one year warranty til the end of July, though I don't think the warranty covers labour of removal/replacement. I'm hesitant to resort to any warranty, as it seemed to work fine when I ran it at the dock (though only for about 20 minutes) and I may be responsible for it slipping anyway for the reasons stated above.

Does anyone have any tips or advice/suggestions? Anything I should do differently aside from what I've mentioned?

Thanks for any help.

Frank

 

[bayhoss]

Frank,
Dark fluid is not a good sign, but not always that bad. It sounds like you have caught the problem early and prevented damage. I would change the fluid once more. Look carefully for any metal flakes or residue. If I found none then I would use the transmission as normal.

Good Luck,
Frank

 

[Emerald]

You're probably OK, but do make sure that the transmission is fully engaging in both forward and reverse. All the cables I can think of allow you to adjust the fork that connects tot the shift lever on the transmission. I would disconnect the lever from the fork and make sure that it really is moving all the way into gear, and then adjust the fork (if possible - don't run out of thread - 5 turns minimum as a rough guide) so that you have extra cable movement when you put it in gear e.g. if you had it in gear, you would be able to remove the fork from the shift lever and move your control at the helm a bit further - the goal is to make sure that you get full engagement and aren't right on the edge, which can cause premature wear, popping out of gear etc.

 

[Frank Langer]

Thanks guys, I appreciate the advice. It sounds like maybe I'll be ok, but I'll change the fluid again, re-check the cable linkage and keep a close eye on the transmission for the next while.

Any other advice or opinions are still welcome.

Frank

 

[mherrcat]

One way to check if the trans is fully engaging might be to shift it into forward then go below to the cable/lever linkage, disconnect it and see if the the lever can be moved any further. My M-18 engine still has the original HBW-50 and there is a definitive feel when the trans engages in forward or reverse. I have never felt it slip.

 

[rwthomas1]

I have a Hurth transmission and there are two holes on the transmission shift lever arm. With the cable of the farthest hole from the shift lever shaft on the arm, the transmission engages but with very little over-travel by the lever arm. In other words, if I shift into gear and then go below and pop the cable off the arm will go farther, in both gears. So I put the cable into the hole closer to the shift lever shaft which results in more "throw" or lever arm travel relative to the shifter on the helm. Shifts very positively now. Clear as mud? Maybe you are not getting enough travel on the shift lever arm? RT

 

[Frank Langer]

Thanks guys. I have re-checked the cable linkage and I'm pretty confident that it is shifting properly into both forward and reverse, and that the cable length and adjustment is appropriate to let it do its thing properly.

I also changed the transmission fluid again today to give it all the help I can. I ran it again in forward gear for about 20 minutes, and all seemed well, so hopefully it will be ok from here on. I'll still keep a close eye on it.

Thanks again for all the helpful advice.

Frank