hi there, i hade the same probplem,ontop of the gear box where the change mechanisme goes in to the gearbox there is a seal which tend to go,i removed the cables and removed the 5 bolts holding the top on,removed the shaft and it was rusted and seized,i simpley cleaned the shaft up and put lots of copper grease on and rebuild and it was like new, quite a difficult job and took about 2 hours but well worth it after local dealer was going to charge me over