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Old 19-08-2012, 15:13   #1
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Hurth Transmission - Need New or Rebuild ?

My boat has a Hurth HBW 250 transmissions (ZF 25M) that is some 25 years old. Last week I belive that I damaged the unit by accidently leaving in forward gear while sailing for about 8 hours. When I discovered that unit was in forward, I shifted into reverse, but with much difficulty. Since then, the transmission is very hard to shift (very stiff at lever) and has on a couple of occasions failed to shift into reverse (linkage "clicks" as if going into reverse, but does not engage).
I have drained and replaced ATF fluid in transmission (four times!) and still see the drained oil very muddy and with metalic dust in fluid. Assume that this is from bronze clutch plates being chewed up.
I have about 16 hours of run time on transmission since the screw-up (and before changing oil). But at this point, 90% of time the transmission will shift into forward/neutral/reverse positions, although with some extra effort at shift lever.

If I rebuild transmission with new clutch plates can I expect normal operation to return? Or have I really screwed up and have no choice but to get a new transmi$$ion? Would love replies from those who have rebuit these units in the past. Thanks.
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Old 19-08-2012, 16:30   #2
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Re: Hurth transmission - need new or rebuild?

Haven't re-built a 250, but have done 2 150s. not a complicated gearbox. Get the manual--and just do it.
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Old 19-08-2012, 16:38   #3
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Re: Hurth transmission - need new or rebuild?

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Originally Posted by Blue Stocking View Post
Haven't re-built a 250, but have done 2 150s. not a complicated gearbox. Get the manual--and just do it.
Thanks.
What were changes in transmission behavior before and after rebuilding? Should I expect improved shifting performance if I rebuild?
Was rebuilding basically limited to clutches?
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Old 19-08-2012, 17:14   #4
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Re: Hurth transmission - need new or rebuild?

Given the total run time circulating contaminated oil you may find damage to most internal parts ie. bearings, seals,thrust plates,clutch plates and gear hard casing. A carefull check of all internals with replacement of all u/s componets should return the box to A1 condition.
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Old 20-08-2012, 22:15   #5
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Re: Hurth transmission - need new or rebuild?

The Hurth/ZF line of transmissions shop manual, showing full details, torque requirements for the various bolts, recommended locktite sealants, etc, etc, is available free for downloading from the following site:

http://www.bukh-bremen.de/files/346/...mechanisch.pdf

It is a German site, but my wife was able to download the English version of the manual.
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Old 20-08-2012, 22:37   #6
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Re: Hurth transmission - need new or rebuild?

From memory the ZF25 is not an expensive gearbox. While it may be straightforward to rebuild and parts may be available I'd be tempted to replace the transmission altogether.

And if a larger transmission will fit why not upgrade? Could save from trashing another.
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Old 21-08-2012, 14:36   #7
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Re: Hurth transmission - need new or rebuild?

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Originally Posted by Boracay View Post
From memory the ZF25 is not an expensive gearbox. While it may be straightforward to rebuild and parts may be available I'd be tempted to replace the transmission altogether.

And if a larger transmission will fit why not upgrade? Could save from trashing another.
The ZF25 list price is well over $3k, but can be found for about $2,000 USD plus shipping (parts only). Not chump change. Would prefer to rebuild and save the money if I can, so I am resisting temptation at this point. If project is doomed to failure I would of course bite bullet and buy a replacement.

The ZF25M can handle more torque and horsepower than I can give it, so don't see any need to go to a larger size (which would involve even greater expense).
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Old 22-08-2012, 14:11   #8
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Re: Hurth Transmission - Need New or Rebuild ?

If you find a dealer that has rebuilt ZF 25-2.0, I would like to buy one. I'm in
Fl. near Port Canaveral. Teamwork
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Old 23-08-2012, 17:03   #9
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Re: Hurth transmission - need new or rebuild?

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Originally Posted by Dennis.G View Post
Thanks.
What were changes in transmission behavior before and after rebuilding? Should I expect improved shifting performance if I rebuild?
Was rebuilding basically limited to clutches?
I've just rebuild mine Hurth 150V.
Spent U$280 in parts. Could do all the work inside my boat if I had a bigger vice.
Not a hard job, just be patient and follow the manual.
If you do everything right, the transmission should work as a new one.
You can change much more parts than the clutches, but, I believe that if your transmission still working, you will not need nothing more than new clutches and new seals/rings.
At least, open it before you order a new one... if you see many parts needing service, maybe is better to find a new one.
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Old 24-08-2012, 05:16   #10
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Thanks Dennis, I had just about decided to do that. Mine won't be done in boat, have a PDQ power cat no room. Teamwork
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