Hurth / ZF M15A Transmission Failures

[Stillraining]

Originally Posted by tomj

Thanks for the note! I've been in "consultation" with several folks from Phasor, Beta Marine, and PYI and have just about come to the conclusion that the problems have stemmed from the damper plate, which is not 'flexible' enough to absorb the torsional impulses of the Kubota engine. Looking at replacing the damper plate with a more 'flexible' unit.......

Good Deal..

That does sort of make sense...

I was at the boat today also and my prop is a 19 x 19 not 17 x 17 as I earlier posted...so I KNOW its not your prop.

[tomj]

Regarding my transmission failures, I've just about convinced myself that the problem is a too 'stiff' damper plate - the original is a Hayes damper - have ordered a less 'stiff' damper from PYI (R&D damper plate) which should dampen the firing impulses of the Kubota engine which has a fairly light weight flywheel. We'll see if this helps once I install the new damper plate. Thanks to Stanley of Beta Marine, Scott of Phasor and Phil of PYI! Will follow up when I get the new damper plate installed, and some hours on the new transmission.

[tomj]

The latest in the ZF 15 MA saga is that I've installed a R and D (PYI) damper plate which is much more 'flexible' than the original Hayes damper. I adjusted the idle to about 900 rpm and things smoothed out nicely. Will have to wait till spring to get some hours underway on the new R and D damper plate coupled with a new ZF 15MA trans (actually has about 12 hours on it with the old Hayes damper plate).

Hopefully this will be the last chapter of a long and sad tale! Next fall "Bahamas Here We Come"!!!

Thanks for all your help and comments.

Tom in Kinsale, VA

[sailalibi]

I am currently in the throws of replacing my hurth hbw10/2r (zf12?) which began slipping just before the last bridge on the icw in Miami! I've been monitoring your progress on the zf15 with great interest. The mechanic (Bill) at TMI here in Ft. Laud says the parts for a rebuild are more than a new zf12 which now makes me nervous. I am planning on replacing the damper plate as well. My engine is a universal 5424 which I believe is a Kubota block so our situations seem similar. My tranny had about 2000 hours on it and I'm told thats about the time for replacement. I hope your luck has changed with the new damper plate...see you in the Bahamas!

Bill and Bess
Alibi II

[Cheechako]

Boy.... I would hope that most would last far longer than 2000 hours. Maybe the older Hurths are a lot better?

[tomj]

I would love to get 2000 hours out of our latest MA15!!! Will do a future post when we get some hours on our installation with the "new" damper plate..... Sure hope we make it to the Bahamas next year!! (We are renting a cottage in Feb and Mar 2009 on Man O War to get our Bahamas FIX!!)

Tom and Kaye in Kinsale, VA

[Stillraining]

Originally Posted by tomj

The latest in the ZF 15 MA saga is that I've installed a R and D (PYI) damper plate which is much more 'flexible' than the original Hayes damper. I adjusted the idle to about 900 rpm and things smoothed out nicely. Will have to wait till spring to get some hours underway on the new R and D damper plate coupled with a new ZF 15MA trans (actually has about 12 hours on it with the old Hayes damper plate).

Hopefully this will be the last chapter of a long and sad tale! Next fall "Bahamas Here We Come"!!!

Thanks for all your help and comments.

Tom in Kinsale, VA

Good luck Tom...I hope to get a 4000 hours and still going strong report from you some day.

Merry Christmas

[RBEmerson]

Sailalibi, I'm not surprised that a rebuild is more expensive than a replacement. The tranny has to be pulled apart, cleaned up, and the case checked out as well as stuffing new parts back into the case. It's faster/cheaper to hang a new box on the back of the motor.

I question the suggested 2000 hour service life, too. We went through two HBW100's before finding out the engine was literally 3/8" too high on the mounts (fix: make new motor brackets that dropped the engine 1" and crank up the adjuster nuts - end of mis-alignment induced shaft, bearing, and tranny failures). In researching the options for a new tranny, I never came across a suggestion that the box was good for only 2000 hours. IMHO, someone's blowing smoke at you on that one.

One point ZF is quite clear about: do not use synthetic ATF. It attacks metal (brass, IIRC) clips in the clutch pack. Just turn the ATF over regularly (every engine oil change) and all should be well.

Added:
The alingment specs call for +/- .004" clearance between the prop shaft flange and tranny output shaft flange. To get the needed clearance, dim-bulb boat wrenches (I hesitate to honor them as mechanics), took the lock nut off the isolators' studs, allowing the adjusting nuts to be run down far enough to bring the engine and prop shaft into alignment. Lock nuts were run down on top of the keeper nuts above the motor brackets, hoping to lock the lower, adjuster nuts into place. Of course, that didn't work, the nuts vibrated lookse, the motor dropped out of alignment, and either the cutlass bearing, shaft, stuffing box, or tranny bit the dust due to the gross mis-alignment. Needless to say, finally finding the true cause of the problem was expensive and didn't do much for the reputation of the second box's installer. Gngh...

[never monday]

Originally Posted by sailalibi

My engine is a universal 5424 which I believe is a Kubota block so our situations seem similar. My tranny had about 2000 hours on it and I'm told thats about the time for replacement. I hope your luck has changed with the new damper plate...see you in the Bahamas!

Bill and Bess
Alibi II

the 5424 was produced from 1977 to 1983. That box has seen a great life. Fit the new one and keep going.

[HASAN]

Dear Tomj ,
I am wondering what is the the last news regarding your trans.zf15MA .I do not believe that changing damper plate will solve your problems.Sorry.

[r.furborough]

Originally Posted by HASAN

Dear Tomj ,
I am wondering what is the the last news regarding your trans.zf15MA .I do not believe that changing damper plate will solve your problems.Sorry.

ZF/Hurth have what they call 'Shock Factor Values' for their transmission when used with 1, 2 and 3 cylinder engines.
for a 1 cylinder engine it reduces the rating by 25%, for a 2 cylinder it is 20% and for 3 cylinder engines 15%. Further some engine manufacturers use a standard flywheel where others add mass to increase inertia and to smooth out cylinder firing on small engine.

Now, with this in mind, the damper plate, if not correctly rated or maybe worn or damaged can have a big effect on the 'shock loads' transferred from the cylinder firing to the transmission.

[RBEmerson]

In the episode with our transmission(s), it turned out that the springs in the original damper plate had either collapsed or otherwise were no longer servicable. Changing the plate, with the transmission already removed, involves some serious grunting and groaning (high torque values on the mounting bolts) but no real technical skill. "When in doubt, swap it out."

[tomj]

Latest installment on the never ending Hurth/ZF 15 MA transmission failure - Check out the following on the Alberg 37 web site:
INSTALLING A NEW TRANSMISSION DAMPER PLATE IN SHEARWATER

Tom in Kinsale, VA

[Stillraining]

Thanks for the update.

[tomj]

The SAGA continues.......

As background, I repowered our 1975 Alberg 37 yawl in 2003 with a Phasor P4-37-05 (37.5 Kubota based engine) with the optional Hurth/ZF 15ma 8 deg down angle trans. I´VE HAD 4 TRANSMISSION FAILURES IN LESS THAN 1500 HOURS ENGINE OPERATING HOURS!!!!! I´m now on my FIFTH transmission!! The last failure occurred back in December, 2009 after we had checked into Bahamian Customs at Green Turtle Cay, in the Abacos, Bahamas

The first (original) trans failed at about 300 hours; the second at about 600 hours; the 3rd at about 250 hours; and the 4th at about 225 hours!! All but the second and last were covered under warrantee by Hurth - but they won´t talk to me anymore - they say there´s something wrong..... I should say so!!! - even though the previous installation of a new trans was performed under warrantee by a certified ZF tech, who called his boss in Annapolis stating ´there´s nothing wrong with this installation - alignment OK, etc. etc. I´ve done the installation on all the other failures myself - (I´m getting pretty good at swapping trans and can do it in about 4 hours (with numerous ´ouch marks´ on my hands and arms!).

The problem in all 4 failures was slipping clutches (in the forward position). The trans specs exceed the engine HP/torque/rpm specs. I´ve rebuilt the trans which was not covered under warrantee, and the forward clutches (8 stack) were considerably worn, along with the ´forward´ thrust washer, which was badly worn.

I´ve been told by a Phasor rep that it appears that Hurth/ZF changed the design of some internal parts about the time we repowered, and that they had ´lots of failures´, and subsequently switched to TWIN DISC transmissions. Of course on my initial failure (and subsequent failures), Phasor told me it was a "Hurth/ZF" matter and take it up with them!!

When I installed the previous transmission, I thought perhaps the original damper plate was too "rigid", and installed a "R&D" damper plate which is a bit more flexible, but it appears that didn´t help much. In my opinion, Hurth/ZF trans are a bunch of ´C--P´


Anyway, anyone have similar failures of the Hurth/ZF 150 down angle trans??? I´m in the Bahamas, and just installed my "spare" transmission, and will probably have the clutch pack replaced (which are worn along with the thrust washers as in previous failures) in the recently failed transmission so I can (hopefully) get back to the US and home to the Chesapeake in the spring. Have no complaints with the Kubota engine - it runs great!

When I get back home, I plan to install a Twin Disc trans, although they don´t make a down angle trans in my horsepower range, which will take a bit of ´re-engineering´.

If interested, go to the following website for photos and writeup of a previous failure (cut and past the below web URL).
INSTALLING A NEW TRANSMISSION DAMPER PLATE* IN SHEARWATER By Tom Assenmacher

Tom aboard S/V SHEARWATER on Man O War Cay, Abaco, Bahamas