Rattling sound in hydraulic gearbox

[ProjectManaia]

Hello all,
Did some research and now I am confident the answer should not be here already...
So we have a sailboat with a 220hp Ford Sabre Engine and a hydraulic driven gearbox.
Recently there is a distinct metallic rattling noise from the gearbox (area) could not track it down exactly yet, however it sounds like a loose piece of Metal (which I reached) rattling around - no luck finding the source just yet...
The other sound I recently discovered is when sailing, as it is hydraulic drive I can't put it in gear so the gearbox keeps turning from the prop side. And a ringing sound starts at low speeds (around 3kn). Sounds just like a small bell being rung...
Any thoughts, ideas and advice would be wildly appreciated!
Thank you all already!
Manuel

[skipperpete]

Too many possibilities to quickly identify without more info but for your first noise, the drive plate is a good starting point, broken or worn springs. The second one is way harder, could be a loose drive coupling or a loose gearbox rear flange but if you have an “aquadrive” CV shaft with a thrust bearing, that’s a contender as well. Rope cutters can make a noise too if the spring thing breaks….. worst case scenario, the propeller is loose on the taper.

[SailingHarmonie]

Without any details, who can do other than guess?

But, hopefully you know that many (but not all!) hydraulic transmissions do not do well when allowed to free-wheel while sailing. Normally lubricated by fluid that is pumped by the rotating input shaft from the engine, they die a very early death from lack of lubrication if allowed to spin without the engine running.

When used in a sailboat this type of transmission requires a shaft brake.

Do you know for a fact your brand/model transmission is designed to tolerate free-wheeling?

[ProjectManaia]

Originally Posted by SailingHarmonie

Without any details, who can do other than guess?

But, hopefully you know that many (but not all!) hydraulic transmissions do not do well when allowed to free-wheel while sailing. Normally lubricated by fluid that is pumped by the rotating input shaft from the engine, they die a very early death from lack of lubrication if allowed to spin without the engine running.

When used in a sailboat this type of transmission requires a shaft brake.

Do you know for a fact your brand/model transmission is designed to tolerate free-wheeling?

I am aware of the "free spinning" issue. While I have the space to put a shaft brake I never got around to it until now... boats, never a boring moment with too little to do,m right?
Anyways, I did (as instructed by a engineer) start the engine every 2 hours for a moment for lubrication.
That being said I never understood entirely... my understanding would be I need oil pressure to engage the gearbox to the engine, so without the pressure the gearbox will spin free, and the movement of gears should move oil around, or not? As I am not aware of a designated oil pump for flow inside the gearbox anyways....? Happy to be corrected on that one though

[deblen]

Sounds like (maybe) damper drive plate.
https://www.trawlerforum.com/forums/...nce-34840.html

[Searles]

Sounds like the drive plate or the bolts holding the plate to the flywheel ,are loose or have failed ,I have personally re built a good number of Borge Warner boxes and reductions ,all failed from free wheeling ,and no the oil in the bottom of the sump isn’t picked up by the gears ,so lubrication fails ,if replacing the drive plate always use new bolts and lock washers ,shaft breaks or feathering or folding props ,usually solves the problem .⛵️⚓️

[rslifkin]

Does the noise occur only at idle and go away with an increase in RPM? If so, it's almost certainly damper plate rattle. If it only happens at idle, the damper plate is likely fine, but the idle is either too low or abnormally rough.

[SailingHarmonie]

Originally Posted by ProjectManaia

I am aware of the "free spinning" issue. While I have the space to put a shaft brake I never got around to it until now... boats, never a boring moment with too little to do,m right?
Anyways, I did (as instructed by a engineer) start the engine every 2 hours for a moment for lubrication.
That being said I never understood entirely... my understanding would be I need oil pressure to engage the gearbox to the engine, so without the pressure the gearbox will spin free, and the movement of gears should move oil around, or not? As I am not aware of a designated oil pump for flow inside the gearbox anyways....? Happy to be corrected on that one though

For Hurth and ZF transmissions of the size that are PROBABLY used in your boat, the movement of the gears is not sufficient to lubricate it. There are a few models that had a “trailing pump” installed and allow this.

This is not meant to be impolite, but your transmission really does not care if you are too busy with other parts of the boat to take proper care of it. If you mistreat it, it will fail, no matter how busy you are with other things. Some things just need to be fixed before a boat goes to sea.

Anyone giving you diagnostic advice is just guessing, since you still haven’t given any details about the engine, transmission, use pattern, boat, etc, etc. But for hydraulic transmissions, you should read all of this thread:

https://www.cruisersforum.com/forums...ff-280063.html

Then you’ll understand the issue if you have a ZF (or Hurth) transmission. If you have another brand you’ll have to do your own research.

If you have a copy of the transmission owner manual, read it. If you do not, get one. It will tell you the proper procedure.