Popping out of 3rd gear

[creation]

On my DC5 it'll occasionly pop out of 3rd gear, this will almost always happen when off the power, typically when coming up to a roundabout, when it does this it doesn't fully pop out and if I try and accelerate I get a grinding noise. I have had this problem for over a year now, I did change the gearbox oil a year ago and it didn't make it any better, it also hasn't got any worse in this time either. Apart from that the gearbox changes in all gears nice and smooth, isn't notchy at all.

Would this be a problem with the 3rd gear synchro, or could it be something else?

 

[stewR]

Sounds like it to me.
From all that I've read recently, I'll be taking my box out soon and replacing the synchros for 3 and 4. I occasionally get an almost pop out of 3rd when changing to 4th, and if I've been using higher RPM and try to change down gears from 4 to 3, it feels like 3rd is locked out until RPM drops low enough or I double declutch.