ZF220 Gear Noise?

[Patrick Mangum]

I noticed this knocking sound coming from my starboard gear.  Link to video on youtube can be found here:

https://youtube.com/shorts/VmrOtDmmbT4?feature=share

The boat ran fine at cruise and no vibrations.  Shifted fine.  Cutlass bearings replaced 10 hours ago and engine alignment done shortly after.  I noticed it as we were coming back into the marina at idle speed.  I’ll have to check tomorrow if increasing RPMs a bit has any effect on noise.  Is this gear chatter?  ZFIRM220A-1  1.235:1  Serial No. 91.3150    6BTA 330

Gear Oil samples taken during pre-purchase in October showed no issues.  Thank you

Topic

[Tony Athens]

I saw this on a 220 gear about 10++ years ago with less than 500 hours on it.. The symptom was “sounds sloppy” when shifting or something like that and the output seal was dripping …..  I disconnected th prop shaft and grabbed the output flange &  pulled up and down as back and forth as hard as I could.. It had about .030″+  movement in it.. Pulled th gear and re-shimmed to a slight preload per the book.. .. I think the factory assembly was off and the aft tapered bearing thrust cone moved aft. That gear is still in service today with 20,000 + hours on it..

[Rob Schepis]

No, not a cutlass, I was referring to a bearing internal to the gearbox.  Like Tony said, very strange noise.  You’ll need to get ZF savvy tech down there to diagnose it..

[Patrick Mangum]

Bearing knock?

Can you please elaborate on what bearing knock means?  Are you referring to the cutlass bearings?  Those were just replaced with Duramax brand bearings 10 hours ago.  I had the engines aligned shortly after to 0.003″ according to my service records.  

Planning on using the boat this weekend and will pay extra close attention to any more noise.  Thanks for your help.  

[Rob Schepis]

Sounds like a bearing knock if it’s following shaft speed.

[Dan]

It might be worth jumping over the side and checking for rope on the shaft, if that fails disconnect the shaft and run the engine in gear.

[Tony Athens]

Very odd sound–Does not sound like typical gear rattle at all..

Frequency at 2-3 “knocks” per second? At about shaft RPM? Very odd.

[Patrick Mangum]

https://www.youtube.com/shorts/POtONHJHMyw

[Patrick Mangum]

New Video Link

I tried copying and pasting the new link to the video and the forum said I was blocked?  

  Raised the RPM a touch and the noise went away.  The last few trips out I didn’t hear the noise at all even at idle RPM and I made a point to check for it.  Normal gear rattle???  Appreciate the help! 

[Rob Schepis]

Video unavailable?

[Tony Athens]

Are you says raising  the RPM a bit helps or does not help?

[Author]

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