High pitch noise - Clutch related?

I am hearing a high pitched noise, which I orignally thought it might be a wheel bearing. But on further refining when it happens, I am thinking perhaps clutch related.

The noise is almost a sustained squeel like noise, rather than a bearing hum, and starts at about 3,000rpm, while driving in any gear. If I depress the clutch and coast, the noise stops. Back under load, the noise restarts, and seems to peak at 3,500rpm although it may just be rising in frequency and engine noise starts to mask the sound at higher rpm or wind noise speeds. It does not make any sound when stopped and revving the engine in neutral.

I have never had a clutch release bearing go in any car I have owned. Can anyone provide some perspective on what clutch related bearings might be making this noise? Drop gear bearings? Not sure how to diagnose with more certainty.

1988 Mondial 3.2 Cab CH88

 

Not sure I understand which hole to put a drop of oil in. Are not the drop gears fully bathed in oil? Is it the drop gear bearings inside there that would make the noise? Or is the noise "normal" when the gears have have worn a bit?

 

So you are suggesting my gear oil is low? I will check, there are no leaks as far as I can tell. When I change the gear oil I fill through that hole til it runs out of the full fill level hole, my understanding is that drop gear area is internally connected to the gear oil sump.

 

Thank you.

I would be surprised that bearings bathed in oil would be failing, at about 80,000km, but I suppose any bearing can wear out.

But as you note the first check will be to ensure my gear oil level is as it should be.

 

Interesting, thank you. It is more complicated in there than I might have expected.

 

I changed the gear oil, it was not obviously low. Used the Redline MTL.

The noise has reduced somewhat, I think. But now that I am sensitive to the sound, I still hear that high pitched sound at about 3,000 to 3,500 rpm when moving under load.