I have a early discovery 2 td5 auto. Having a problem with the automatic gear box. About 6 months ago I changed the gear box oil, ran it for a few hundred miles and changed gearbox filter and oil again. Everything good up to a week or so. The box seems to be changing up through all the gears ok ( sometimes a bit slow changing up) but main problem is once in top gear the revs stay high. It used to always feel it had changed up another gear when the revs dropped down but it's not doing it anymore. Checked level of oil and all good with no burnt smell. Has anyone got any ideas what it could be. Thank you in advance for any help you guys can give