A couple of times recently I have found that when I have been on a trip of say 25 miles plus and everything is hot, the 5 speed manual gear change can become quite stiff/notchy. Normally the gearchange is perfectly smooth from cold and no problems at all. The gearbox oil is supposed to be for life but I wonder if it is somehow getting tired or maybe even leaking a bit - if the oil was a bit low then I could understand it beginning to cause a problem. Any body else found this? It is an Audi A4 Avant 2.4 V6 petrol just nudging 100K miles and otherwise flies along the motorway in a still impressive silky smooth manner.