I bought a 2019 next gen 308 a few months back. It has 1450 hrs. Machine was always well greased and maintained prior to me owning it. The issue I’m having is a little odd and maybe nothing to worry about. When swinging the bearing feels tight and smooth. Although the brake or the swing motor sounds like rice krispies when braking quickly. When swing at slow speed, you can hear and feel it, it’s almost not noticeable. It’s a faint sound and feel even when swinging quickly. Had anyone heard this sound before? Anything I can check?
These usually have a "cushion valve" which is part of the slew motor circuit and they are noisy, I'd say more like a hissing and gurgling noise (similar to cavitation), assuming rice krispies go snap, crackle & pop like rice bubbles do down here. When the cushion valves fail completely you'll get noticable uncommanded slew in the direction of gravity after you centre the left joystick. That's not happening in your case is it? If you wan't more detailed info we'll need a s/n, there's a few types of 308.
It won’t be the brake because the brake doesn’t come on until after you’ve stopped swinging. Check that there is grease in around the pinion to swing gear contact area. If we get a serial number we can get a better picture of how to inspect that.
Actually, the swing brake is the first thing that came to mind for me. The swing brake is just a "parking" brake. I can't exactly remember what the time period is on a 308 but lets say that the swing brake engages 5 seconds after the pressure switches on the pilot lines of the swing section read no pressure. Like Chrisso said, it is actually the hydraulic oil dead heading that stops the machine from swinging. I have heard a lot of descriptions of hydraulic problems but never "rice crispies" To me that sounds like brake drag since the op feels pretty sure about the condition of swing gear and bearings. The swing brake is spring applied and hydraulic released. If it was in my lap the first thing I would do is add more grease to the turntable. Then I would plumb into the swing brake line to see that I had adequate pressure to release the swing brake and that the pressure wasn't bleeding down.