Hi there,

Today I took a 50 miles trail and, on the way back, suddenly, my Zforce 1000 (1500 mileage) started to make a constant CVT like noise. Not just on deceleration (as normal) but on acceleration too, which is very weird and never happen before (nor on Z1000 or the other machine, Z550).

In addition, the higher RPM is, the louder the noise, until it reaches a whistle.

I attached a short video for documentation.

What could cause this noise? I thought that's the belt but on idle the noise is not present.
Could it be low level of oil in rear diff (the noise comes from rear) or the gearbox (a bearing)?

https://youtu.be/F5QLYPZdGNk

[2015 Z Force 800 53/Trail EPS]

If that's just in 2wd then I would say your rear gear case (diff) pinion is developing a problem. Better check the lube level, then change it. Inspect the old for metallic fragments. Also check the movement and back lash of the pinion.

Welcome to my world. Mine has been chewing itself up for the last two years and been getting louder and louder. NOT as loud as yours yet but about the same sounding play between power on and off. I think I'm loosing a pinion bearing...the inner one and I change my lube now every about 300 miles with 90w140 conventional. It helps with the noise and slows the aluminum filings I'm getting.   

Thanks NMKawierider,

I too suspect the low oil level (although I have only 300 miles since the last change but almost a year) or a bearing.
I'll check the oil level this weekend and hope that's the reason.
The noise is the same in 2wd and 4wd.

Have a good year!

That is how our Z8 has sounded since we got it.  I've changed the diff fluids every 500 miles and never seen metal filings at all.  Currently, 1500+ miles.

My 800 Trail with +8000 Km (5000 Mi) makes that sound but only in high range between @30-42 KMH. Never seen glitter in my oils. I call it 'The song of my people.'
Odd that yours has just begun to make that song. I don't know what to make of that.

My 2018 800 has made that same noise from day one. Never given me a problem. Fluid changes look like new oil. 🤷‍♂️🤷‍♂️

Odd, CVT are normally a  little loud on some machines I notices the 800s over my 500 had a big difference.

If I were you I'd Crack open the case and take a look so see if there's any debris, blow it out and taker back for a ride.

That is if your CVT isn't a wet one. Mines dry.

It's strange because the noise started suddenly. I have this machine from 2018 and never heard that noise till now. Also my Z500 (2016) doesn't make that sound (more than four years old and 4000 miles).
Anyway, i sent the Z to the dealer and they said (at the first glance and without making any checks) that the noise could come from the clutch (last year, when they replaced the gearbox under the warranty, the mechanic re clocked the clutch upon my request).
I told them that the noise doesn't come from thee clutch but rather from the gearbox or rear diff. Now I'm waiting for their conclusion.

It is possible that a reclocked clutch to make that noise (the new position is B2, not very extreme)?

I've got the answer from the dealer.
The gearbox was on "oil vapors" .. almost zero oil. They added the oil and the noise disappeared.
Now they are trying to figure out where it leaks    I have 400 miles since the last oil change (and around 10 months).

[2015 Z Force 800 53/Trail EPS]

You would have seen an oil leak. Wonder how much damage it did.

Pfff ... That is exactly my concern now.
Have any idea how much would cost a gearbox?

Update.
After 10 days in dealer's shop and complete disassembly of the engine and gearbox, they found the problem:
Last year, when the dealer replaced (under warranty) my gearbox, the "top mechanic" who was in charge with the operation, forgot to replace the gasket (or broke it in process) and the oil simply leaked all. After a close inspection it came out that two bearings and some gaskets need to be replaced.
After a long fight (over phone and email) they agreed that this is their fault and will pay for the repair.
I hope this will end soon and I get my machine back in time to get a few more rides in snow.

Keep safe and out of troubles!