I've got a DHX 3 Air rear shock which has started squeaking, it was serviced last summer and has locked down in the past.
It only seems to happen on very quick, harsh compressions – like square edge hits and is a very audible high pitched squeak.
I run the shock at quite a high psi (~200), is it anything to worry about or maybe just a lack of fluid in there?

Maybe give the air can a service? Very simple to do.

what kind of squeak? could it be the rapid transfer of air through valves?

yeah, I've done the service before and not that long ago
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it's definitely the kind of squeak you get when air is passing quickly through something rather than two surfaces rubbing together – it's like when you put your thumb over the end of a bike pump and push hard

My RP23 was doin something similar. Spoke to Mojo and they said it might be the shims inside the shock. Got it serviced and it seems ok now. Not been used in anger yet but hope to get out tonight.

sounds like it could be a normal noise you would expect from the compression or rebound damping systems then. if you're not losing pressure or having any problems then i would say it's fine. couldn't tel for sure without listening to it first hand though. high pressure = high pitch makes sense.

Last summer my rear shock had a asthmatic wheeze right up until the point it packed down, after a visit to Mojo it has been fine

thanks, it's probably nothing then
maybe I'll take the air can apart and make sure everything looks ok, maybe add some extra oil