Pilot Bearing Noise?

[Bongani]

How can one determine if the pilot bearing and the release bearing is warn or getting old?

My truck has 120 000km on the clock. On cold mornings I can hear a slight rumble that dissappears when I engadge the clutch. When driving I can hear the occational gwhrrrrrrr sound that lasts for about 3-5 seconds and it sounds as if it is coming from the front. The gwhrrrrr sound started after I went playing in the sand.

Bearings, birfields, U-joints, spline yoke are fine and props have been balanced. New tyres were also fitted. Problem stayed throughout all these checks and changes.

 

[sixsracing]

So many symptoms, so little space.
Pilot bearings will:
cause a grind when shifting into first or reverse from a stop.
howl when at a stop and clutch pedal is not depressed.
cause vibration under load and startup from stop.

Throw-out bearings will:
grind, howl or crunch while depressing clutch pedal
cause a vibration in pedal while depressing clutch
howl when at a stop and clutch is not depressed.

Unfortunately some of these symptoms are the same for both items. General rule of thumb is that if it makes noise with the clutch depressed it is the throw out bearing, without the clutch depressed it is the pilot. But this is not a concrete rule. Sorry to be vague but sometimes the only way to determine where the actual noise is coming from is by invasive surgery.