My 2004 6-speed mondeo has just started popping ouf third when slowing but is ok when accelerating. Is this a 'linkage' problem or an expensive syncro replacement please?
It could be a number of things. I'd recommend taking it along to a garage asap and having them assess the cause. As the problem sounds like it's easy to reproduce itshouldn't take them long to establish the issue.
This is usually due to wear in the gearbox - gear teeth are not straight cut so there is an axial thrust which will tend to push out of engagement on overrun and into engagement on acceleration, or vice versa.