Hurth tranny, 4 years old, kaput

[jen1722terry]

Hey sailors!

Well, we got our 31 in the water late this year up here in Nova Scotia. We planned to leave for Cape Breton (Bra D'or Lakes) on Tuesday, but the tranny would'nt stay in forward (Hurth model ZF-10-M, new in 2011). This problem appeared sporadicaly late last season (after 1200 miles of cruising the last two summers, mostly powering). The problem would disappear once the engine was warm.

We have an excellent mechanic up here and he recommended changing the fluid, which we did two weeks ago. Old fluid was dark brown, nearly black.

After much adjusting of the shifter arm and other tests the tranny was pronounced in need of rebuild. As the parts, labor and delay would be significant, we opted for a new tranny of the same model (about $1900 US up here). He also recommended we order the tranny with a transmission fluid cooler installed to extend the life of the unit. He said such problems are not rare for folks who motor a lot. I also noted that our engine (U-M25-5421, 1984) tended to run a bit hot over 2200 rpms before we intalled the new, 3" HX in June).

The wisdom we seek from the Cape Dory community is:

1. What can we do to avoid future tranny failures, in addition to adding the fluid cooler on the new unit?

2. Has anyone else experienced problems with the Hurth ZF-10-M?

3. If we bring the old tranny, (same model) back to New Hampshire with us in the fall, does anyone know of a reliable mechanic who can rebuild it? If so, would the rebuilt unit have enough value warrant the trouble?

Lastly, thanks to all for the recommendation to upgrade the HX. Our old M-25 now purrs along at 155 degrees, even up to 3000 rpm and beyond, when we need the extra power. Nice.

OK, back to breakfast with Jenn and looking forward to the arrival of 15 wooden schooners today in our little harbor (Mahone Bay, south of Halifax). Many camera shots lie ahead.

Happy sailing to all.

Jenn and Terry

[Ken Cave]

Foley marine, among others, have some great articles concerning Hurth Transmissions. I have the same one you have, and am on my second engine with it. My first engine (A Volvo 2020) was installed in 2000, and the instructions said to use 15-40 weight oil, same as in the engine. I just replaced the engine this past year with another Volvo

After a couple of years it was getting "cranky" so I asked Volvo why they insisted on using engine oil in their transmissions.
Their answer was that it was available and one would change the oil more frequently.

Foley says to use synthetic transmission oil, and I have done so for the past thirteen years, changing the fluid once a year.
No problems so far.

It seems that many of the charter fleets had your problem, and that was when it was discovered that synthetic transmission oil would solve the failures.

Hope this helps

Ken Cave
CD 28

[JWSutcliffe]

Have used ATF for 7 years, and never had a problem - even with extensive motoring times. If the lubricant is badly discolored, it may indicate that the clutches are either worn or not engaging properly due to cable misadjustment.

[jen1722terry]

Thanks so much to Skip and Ken for the comments.

We two hours with the mechanic going over all the troubleshooting scenarios in the Hurth manual and the final diagnosis was worn or otherwise damaged clutches. The rebuild time and cost versus the shorter delivery time and warranty, in addition to getting the oil cooler on the new tranny, swayed us towards a new unit.

We may have just gotten a bad one. We do like Ken's comments about the sythetic fluid in the charter fleets. We'll try in in the new one.

Thanks again, and we'll keep all posted on how the install goes.

[Maine Sail]

I have yet to see a failed Hurth/ZF that always had clean ATF in it. This is not to suggest that it can't happen, just that every failed Hurth gear I have seen was what I would consider poorly maintained. The fluid should never be black or even light gray for that matter. I have these gears out there with well over 4000 hours but these have had the fluid changed at a bare minimum of 1 -2 times per year. With my own ZF Hurth it is done fall, early July and late August... Cost me about $4.00 each change...

Unfortunately you are now likely in for a rebuild or new one I would strongly suggest you call Stanley at Beta Marine USA and get a more durable gear. Stanley has one that will literally bolt in place of the Hurth/ZF, and they are less money!

The gear that Stanley has/sells is called the Techno-Drive TMC-40 which is also known as the Twin-Disc MG-340. It comes in a 2:1 or 2.6:1 ratio and it costs $1144.00 BRAND NEW.. You'll also need the shifter bracket but all in you are under $1200.00 for a better built gear, with warranty and brand new. Also don't forget the damper plate, Stanley has these too for far less than Universal/Westerbeke...

Why are the new and rebuilt Hurth/ZF gears not lasting as well as the old ones and why do they require very, very frequent ATF changes?

The thrust washers on the Hurth/ZF gears used to be real solid bronze. Now they are steel coated with a sprinkling of fairy-dust bronze. They are no longer a solid bronze thrust washer as they should be! This is a literal joke of a cost cutting measure by ZF... This fairy-dust coating does not make for a true "bronze thrust-washer". As a result if the fluid gets dirty, even a little bit, that fairy-dust bronze coating disappears QUICKLY and then you are steel on steel, and your gear is DONE in short order!

If you own a Hurth/ZF gear PLEASE, for your own benefit, DO NOT EVER allow your gear fluid to be anything other than a fraction of a shade off what it came out of the bottle looking like. This usually means at least one or two changes per year.

I also own a Hurth/ZF but the fluid is changed 2 - 3X per year at a cost of $12.00 total. Short money to keep an expensive gear going strong.

The fairy-dust thrust washer........

[jen1722terry]

Thanks so very much to Maine Sail who, as he has many times before, has taken the time to educate us struggling skippers with very thoughtful analysis and advice.

The steel thrust washers could very well be the problem with our forward gear in our Hurth ZF, especially given the symptoms and the fact that we only change the fluid one each year in the two years we've owned the boat (putting about 230 hours on the engine). If they're no longer bronze, it's not surprising they would fail.

So, what to do now?

Our new Hurth ZF-10M-R is due in from Toronto today. What we plan to do is call our mechanic and see if he can return it at our expense and get the Beta transmission. We know he's familiar with Beta products for he just installed a new Beta engine and tranny in our neighbor's Alberg 37.

This may mean doing without a reliable engine for another week or so, but with plans to go up to Bra D'or lake in Cape Breton this year, the Downeast Circle next year and the Bahamas the year after that, It may be worth the wait for the peace of mind.

I also plan to call Hurth today and ensure that the newest ZF-10's still have steel thrust washers.

Our only other choice is to get the new Hurth, installed with the oil cooler on the new unit, change the oil at every engine oil change (50 hours for us) and hope for the best, keeping the rebuilt old unit on board as a backup while we're cruising.

The bright side of all of this is that, while we're stuck at our mooring waiting for the repairs, our little town of Mahone Bay here in Nova Scotia is hosting Schooner Race Week at the town wharf a 100 yds from our mooring. 10 wonderful old wooden two-masters are there as I write this - a site to see and we'll post some photos when we get the time.

Again, we can't thank Maine Sail, Skip and Ken enough for taking the time to share their wisdom.

Happy mid-summer sailing to all of you. We'll keep you all posted on the repairs

Jenn and Terry

[Maine Sail]

Just be aware that the Techno drive is a tad bit wider and if your stringers were sized for an Atomic 4, it may not fit in between them. This is the only complaint I know of with this gear... Call Stanley at Beta USA and he can walk you through it all. IIRC the TD is also about 3mm higher on the coupling but nothing that can't easily be solved with alignment.

Good luck with ZF. Last time I called trying to get a real solid bronze thrust washer they assured me they were bronze. When I ordered that part it was "fairy dust" coated steel NOT bronze. Apparently the right hand does not know what the left hand is doing at ZF. A while ago I found a source for a bronze thrust washer of that size but I can no longer find it...

[Phil Shedd]

Never say die with these transmissions.

This past year I have had the transmission out of the boat three times. Last fall to rebuild it because it was slipping in forward. I bought the rebuild kit and did it my self. It took a long time to get it out and back but all seemed well. When we launched in the spring I had forward but no reverse. When I say no reverse I mean it stopped the engine. So out came the transmission and I found I had placed a disk in the wrong order. This was fixed and the transmission was put back in. All seemed well until one day I had no forward. I had reverse but it would not go into forward regardless what I did with the linkage. So out it came again. This time I found the real problem also I think the one that caused it to slip last year.

The shifting fork fits in a grove which is part of the shifting plate . When you engage the transmission the fork moves the plate so it will cause the clutch plates making the transmission go into gear. What I found was the fork was worn on the forward side so that it would not move the shifting enough to cause it to engage. I rebuilt the shifting fork by making sure there was very little play in the grove. I put everything back together and back in the boat. The transmission works as it should.

These units are very simple easy to repair and should last a long time. I do not think mine had been rebuilt before .

The first time I took it out it took three days out and four days to get it in. Second time out it took a day to get it out and two days to get it in. The third time it took 2 hours to get out and 6 hours to get it back in . There better not be a forth. I did not remove the engine but lifted it up about 6 inches so I could get at all the bolts.

So do not give up on the unit rebuild it and put it back.

Good luck
Phil

[jen1722terry]

Thanks Phil,

With a bad back, it's enough for me to change the fluid and check the cable adjustments, let along pull the tranny and rebuild it. I used to be a decent car mechanic, but that was back when cars had no computers and lots of elbow room under the hood.

I was first thinking that we'd get a new one here and take the old one back to the states for a rebuild (we live in Nova Scotia 6 months/year but are Yanks from NH). But labor is cheaper up here and, with the very strong US dollar, cheaper still.

What we may do is have our mechanic rebuild it in the fall, but with bronze thrust washers, which we'll have made at a local, very reliable, machine shop. The mechanic can also let us know if other parts are needed that we can order or have made. We'll then keep it as a spare, for we plan several long cruises (Maine, DownEast loop, Bahamas) in the next few years and a spare on board may save time and money (particularly in the Bahamas). At the very least, we'll carry a rebuild kit with bronze thrust washers.

We liked Maine Sail's recommendation to install the Beta tranny. But they're expensive over here in the Maritimes and shipping from the US also jacks up the price with the import duties. He felt that, if we changed our fluid often, the new Hurth would hold up. We now plan to change the tranny fluid every oil change, in addition to adding an oil cooler on the new tranny. With the neat little pump we bought, the oil change is about a 15-minute job.

So we'll stick with the devil we know and stay with the new Hurth ZF-10, due in yesterday (Nova Scotians have a bit of a "manana" approach to time). Maybe this time we'll get lucky

Thanks again to all who commented. We'll keep you posted on the new install and diagnosis of the old one.

And to all the other members: remember to change your tranny fluid!

And do enjoy the mid-summer cruising,

Jenn and Terry

[jen1722terry]

Hey CDers!

The new ZF-10M-R is in the boat and it now shifts fine.

We're still waiting on the oil cooler to (hopefully) protect the tranny in hotter weather.

It was a project, in that the engine had to come out. It seems the ZF-10 is bolted on from the inside of the bell housing which, according to our mechanic, is not the usual way to do it. To get to all the bolts, he had to lift the engine and pull it out, adding maybe 4 hours of labor.

He will rip down the old one and see if the problem was, in fact, the steel thrust washers. If so, we'll get bronze ones from the states or at our local foundry up here. We'll try to get a lot of them, if possible, for other ZF-10 owners who may have the same misfortune with this popular, but fragile, gearbox.

And, of course, we'll be changing our fluid every oil change, as the dirty fluid may have been the culprit. We also plan to fill the tranny for winter layup. The manual only recommends this for storage over one year, but they also recommended changing the fluid "at least once a year".

All else well. Sadly, it's probably too late for us to cruise up the Nova Scotia coast to the Bra D'or lakes. But we're planning to start the Downeast Loop next June, going from here in Nova Scotia down to NYC then up to Lake Champlain, where we'll cruise until it gets too cold and lay her up in Burlington, VT. We'll complete the loop the next summer and do the Bra D'or lakes on the way down the coast.

All else well. Email if you have any more technical questions about your ZF-10M, as we're becoming quite knowledgable on them. Thanks again to all for the patient and very sage advice.

And happy August sailing to all of you!

Jenn and Terry McAdams

[Steve Laume]

I had to have Raven's transmission rebuilt a few years ago. Her engine also had to come out because some brilliant engineer decided to bolt the thing on from inside the bell housing which is also incorporates the engine mounts.

Not to suggest you might be miss treating your trans but you never know what a PO might have done. For my transmission it is recommended that you leave it in reverse when sailing. This pretty much removes the prop locking debate for me. The other thing that comes to mind is when I crewed for a guy a few years ago. I don't know if he was raised with single lever controls but that is how he used his boat. Throttle in the mid range and just shift at will. I cringed every time the thing we into gear, Steve.

[jen1722terry]

Thanks for the thoughts, Steve.

We think we did not change the fluid often enough, for the hard running we did bringing the boat up from Annapolis to Nova Scotia.

Also, the boat was in the Chesapeake heat for the first two years of the tranny's life, with no record of anything other than annual fluid changes. So it goes.

Our mechanic feels that the addition of an oil cooler (due to go in tomorrow, we hope) and religious fluid changes will lead to a long life for the new unit, even if we take her south to the Bahamas. We hope so.

And our transmission was also bolted on from the inside, as is the new one. Our mechanic said it had to be done this way, and we're not mechanically erudite enough to argue with him. The old M-25 had to be hoisted out onto the cabin sole for the switch - it made a nice coffee table for a day.

$3800 Canadian poorer, including their sobering 15% sales tax and labor. A hard lesson, but one that will not be forgotten.

We're now thinking about how to get the old one rebuilt: up here or down in the states? Any recommendations for rebuild shops would be welcome. We're also going to try to have the stepped steel thrust washers copied up here in bronze for the rebuild by a friend who is very adept with a metal lathe (he builds world-class models for maritime museums).

Thanks again for the thoughts. Happy sailing and maybe we'll hook up next summer when we bring the boat back Down East on our first leg of the Down East circle cruise.

Jenn and Terry

[Steve Laume]

The extra fluid capacity gained by adding an oil cooler may be as valuable as the increased cooling.

[jen1722terry]

Yeah, Steve. I hadn't thought of it that way. An added bonus.

We'll update on the cooler installation and final cost tomorrow. We still have a few months of sailing up here in mild Nova Scotia, and we're itching to get to it.

After haul out, we plan to start on the ice-box insulation and refer installation project. Maybe paint the decks, though that can wait until spring. Jim Walsh's post on leaking water tanks has me itching to take out the saloon berth decks and see if that is the cause of a persistent slow leak into the bilge (it better be, we've looked everywhere else). We may replace the sani hoses from the head on out (we'll see what they look like inside first.
Always things to do, some planed, some not. Such is sailing.

Have a great weekend.

Terry

[jen1722terry]

Just a quick FYI on the install of the oil cooler on our new ZF-10M-R tranny:

The oil cooler does not increase the transmission fluid capacity of the tranny. It is basically a small, hollow metal box, 4x5 inches, with an inlet and outlet port to move seawater past the surface of one side of the tranny, cooling by conduction. Let's hope it works. Boat now runs like a top. Let's hope it stays that way.

Off to go sailing.

Cheers!

Terry