My 1989 9000s automatic broke down on the motorway. The engine was running fine but it was as if the gearbox jumped into neutral. I was ready to scrap the thing as I thought that the gearbox had blown, but a friend reckoned it could be the inner CV joint. Anybody suggest how I can diagnose this problem. I can fix the CV joint myself (done one before) but draw the line at forking out for a new gearbox.