So at BPW today my rear Deemax hub was making a loud buzzing noise when freewheeling. Kind of like a brake rubbing but it wasn’t.
The noise only happened at speed and would stop as soon as I started pedalling…

Anyone got any thoughts?

Death scream. You’ll need to take off the freehub and clean, lube the main nylon bearing. This may save it for a few weeks, possibly months.
It’s a common Mavic issues and loads online about it.

That sounds like it..I’ll give it a strip/clean see how it goes. They only get used occasionally.
If not I’ll have to try and work out which freehub to get.
Cheers o&o

You can buy a replacement nylon bearing for much less than a complete freehub.
They’re easy to fit and last an age.
Have a look on eBay for hub Dr

Make sure you use mineral oil in the freehub.

Mineral oil or I used finishline wet lube. Made it last a good few months.

Mostly it’s wear to the inside of the freehub and the machined boss on which it runs, which holds the pawls and springs. Look carefully and you’ll see the score marks. It’s this wear that is allowing the freehub to oscillate, which sets up the noise. The nylon bush only bears on a rubber seal so I don’t believe that’s the culprit. I found slight play on my freehub so I cleaned it up and re-lubed with engine oil and it’s running fine. The oil has taken up the gap and you can’t feel any movement.