Kanzaki transmission high pitched noise

[dial_amonkey]

I'm wondering if anyone can suggest what might be causing a high pitch noise originating from my Kanzaki Kmp35P transmission:

The noise has always been there but has steadily got louder and I can no longer ignore it.

I eliminated the driplesss stern gland - I greased it and burped it, there's no air trapped.

I'm dreading it's gear lash noise (but I'm no expert)..

The noise is most noticeable at around 2000 rpm and then seems to disappear at higher rpm. Nothing in neutral or reverse.

Seems to come on when running engine so nothing at first then as the transmission warms? but not sure about that

Thanks for input or advice.

Unfortunately I was not able to upload a sound file (cruiser forum does not allow me to upload) I'm looking for a way to link to a file...

[Mirage35]

I know roughly nothing about transmissions so can't help immediately.

But as noted in another thread recently I have the service manual for that transmission. If you get to the point where it might be helpful, PM me with an email address and I'll send you a copy. (Same for anyone else who is interested.) Can't upload it because it's a bit too big for the site limits.

[skipperpete]

Start with the simple things, change the oil and inspect it closely for metal particles, check the position and travel of the selector arm. Get a flashlight and take a peek through the cooling air grille and inspect the drive plate. Some of the engines that had this gearbox also had a cooling fan attached to the flywheel, it could make a whining sound..... it’s a big fan although if there’s nothing in neutral or reverse it does narrow the field a bit.
Here’s one that had me beat for a while.....same gearbox, noisy in forward but quiet in reverse so I undid the coupling to eliminate the propshaft as the culprit and the noise ceased BUT the gearbox flange nut and shaft was unusually shiny. Turns out that the shaft had moved forward in the coupling or had been assembled that way in the past and the propshaft was hitting/butting the end of the gearbox output shaft. We moved the coupling 12mm further up the shaft, re joined the coupling and the noise was gone and to this day I can’t explain why.
Logically that shaft and the flanges should work as a rigid assembly and it shouldn’t matter that the shaft butted the gearbox but it definitely did.

[dial_amonkey]

I tried a few more information/troubleshooting steps:

Ran the engine up to 2K rpm WITHOUT the drive shaft attached - to try an eliminate the shaft seal and cutlass bearing : No noise (But most likely engine needs load to generate gear noise?)

Attached dock hose to shaft log water feed, forced water through shaft seal bearing: Noise was still there may have been slightly less - but not sure.

With the shaft unbolted from the engine and pushed out towards the rudder, I inspected the cutlass bearing end of the shaft underwater - it was 100% clean no corrosion

Thanks for the suggestions SkipperPeter, : I changed the oil recently, but I'll do that again to check for any metal particles. Also will make sure the selector moves correctly.

It's easy to remove the transmission so might take a look at the fan and damper plate to see if it's anything unusual.

[skipperpete]

Originally Posted by dial_amonkey

I tried a few more information/troubleshooting steps:

Ran the engine up to 2K rpm WITHOUT the drive shaft attached - to try an eliminate the shaft seal and cutlass bearing : No noise (But most likely engine needs load to generate gear noise?)

Attached dock hose to shaft log water feed, forced water through shaft seal bearing: Noise was still there may have been slightly less - but not sure.

With the shaft unbolted from the engine and pushed out towards the rudder, I inspected the cutlass bearing end of the shaft underwater - it was 100% clean no corrosion

Thanks for the suggestions SkipperPeter, : I changed the oil recently, but I'll do that again to check for any metal particles. Also will make sure the selector moves correctly.

It's easy to remove the transmission so might take a look at the fan and damper plate to see if it's anything unusual.

You should have a little window on the gearbox housing to look through to inspect the drive plate and there’s only a slim chance that you have that fan, it was only used where the engine horsepower was close to the gearbox rated capacity, a 3JH is well below that.

[dial_amonkey]

Checked the alignment - my mechanic friend suggested a different method for checking the alignment: But I'm certain it's under .010 mm runout

Mechanic friend also suggested turning the rudder with the engine at 2000rpm and if it's an alignment issue the pitch should change : Nope no change

Yes: There is a fan of sorts in the 'Clutch Flange' = gearbox housing, it's possible the noise is some sort of resonance of the fan, but does not seem to be that sort of sound.

Gear shifter moves correctly, greased it anyways.

Thanks for suggestion SkipperPete: Nothing unusual in the coupling, center bolt tight, shaft in the correct place, nothing looks out of the ordinary.

Uploaded to Youtube:

https://www.youtube.com/watch?v=nM9QMj0owv8

[Jim Cate]

Does the frequency of the whine change with RPM?

Jim

[dial_amonkey]

Yes it does change with RPM..

https://www.youtube.com/shorts/Rd1IpyT-zrE

[Scubaseas]

Sounds like gear whine to me. Usually caused by slight bearing wear which makes the gears ride differently than when not making noise. Not aware of any additive or fix other than replace bearings and to have a really good hard look at the gears involved in forward. Might be a roller or needle bearing issue on the countershaft but it really sounds too high pitched for that. Probably not going to fail catastrophically but not going to get better without replacing stuff. Might last a long time but if it increased recently the more noise it makes the more I would want to pull it out and take it apart. I have the same gearbox and it's got a slight whine to it but not like what you have.

[dial_amonkey]

I tried a few more information/troubleshooting steps:

Changed the oil : No particles of metal sparkled in the sunlight when the very last bit of old oil from the transmission was spread on a paper towel (the black was from news paper underneath)

The Kanzaki KM35P sump plug is not magnetic!

Physically pushing the engine slightly sideways (changing the alignment) with the engine at 2K rpm didn't change the pitch of the noise

[Mirage35]

I might have it this time - I have broken the manual into separate files to fit the upload limit: General information for the family and overhaul procedures for the KM4A and KM35P.

[skipperpete]

Thanks for the download Mirage35, much easier than scrolling through the service manual.
I guess the O.P has now found the source of the gearbox whine, but if not, consider the possibility of a wrong rotation propeller and a situation where astern has been delegated to ahead. With this and numerous other mechanical reduction gears, prop shaft rotation in ahead is clockwise, viewed from the rear (not negotiable) , if reverse is selected as continuous ahead operation, the load is carried by a longer string of gears ( all gears in the drive train spin in constant mesh but in ahead the loaded “teeth” is dramatically less)
Just an afterthought, : -).