Gearbox guru's......

[Milestone]

Good evening, this is for any transmission specialists out there! I have an old Hurth HBW 125 gearbox attached to a nanni 37.5hp. When the engine is idling, or in drive up to moderate revs, there is a high pitch whine that comes in and out. The noise is like air in a hydraulic system, and more noticeable at the oil pipes going to the cooler. I have changed the ATF in the box, which made no difference.

Now I know Hurth are discontinued, and the box is identical as a ZF12M. What I don't understand, (as of yet I haven't disassembled the transmission), the transmission is a mechanical type not hydraulic, so doesn't have an oil pump. But the oil cooler for it is supplied by 2 oil pipes from the box. So how is there flow? Is the incorrect cooler fitted? (All the literature I have seen for the ZF12m box is the cooler us direct on the gearbox)
I haven't got any photos at present but can get some.
Hope this makes sort of sense

Regards Ben

 

[Eeyore]

I cannot see how the gearbox supplies oil to the cooler which is bolted direct to the box. The two pipes going in/out are for the cooling water. I had a Hurth HBW 125, then replaced it with the ZF12M - neither had a cooler fitted and as I understand, providing you run at 34Hp or under, a cooler is not needed.

 

[Milestone]

Thank you Eeyore, they're definitely oil lines coming out,as I cracked off the union and oil came out. Like I said, I can't see how it would work with out a pump. I may remove the lines and put blanks in to see if the noise disappears. Thanks again

 

[chrishelen]

Hi. I have a zf10 or hurth 100. Great little boxes. I have the same noise as you are describing. Mine comes in at 1200 and dissappear at 1800. When I first got the boat about 4 years ago I was quite worried as its a commercial boat, but I had various experts look at it, and we even put a spare box on, noise still there! We put it down to harmonics from the prop. I do 100 of hours a month.

 

[Milestone]

Hi Chrishelen, I can get the noise in nuetral and just at idle. Also I think it may be temperature related, yesterday didn't do it till it warmed up.

 

[chrishelen]

Hi Chrishelen, I can get the noise in nuetral and just at idle. Also I think it may be temperature related, yesterday didn't do it till it warmed up.

Strange. I know the bigger boxes are water cooled. The guy who knows all there is to know about these boxes is 'Jez' at pilkinton marine. Haven't got his contact details as they are on the boat. A quick Google search will bring him up. A most helpful outfit, good luck.