l was driving on the motorway at 80mph and my car slipped out of 5th gear, it then went back in quite easily but a moment later it happened again.this happened about 3threes and have not tried to put the car in 5th gear again.could it be something like the gearbox oil needs checking or could the gearbox be on its way out

If its jumping out of gear on the overrun?That is when you are taking you foot off the accelerator?then its the gearbox on its way out.Oil lubricates it, and keeps it quiet?You do not mention any funny noises?Hope this helps

Check if the end plate of the gearbox has a steel plate/cover if so remove the retaining bolts and remove the cover,this then gives access to the 5th gear hub,A staked nut on the end of the shaft sometimes comes loose allowing the hub to float. This was common on 405s but as its been a few yrs so l may be completely wrong but it is worth a look..

pug di boxes were never the best.if it was gearbox oil it would be sqeeling in 5th gear..selectors are worn.