Lee007

Hi guys,ive got a problem with my uk 2000 wagon,it decided 2 throw 3rd gear a couple of days ago,so sourced a second hand box and got a mate,whos done a few newage boxes 2 fit it.After it was fitted he found the gear linkage that is pinned on the box didnt fit my gear linkage so he had 2 swap it with the one off the old box,this made the gearstick sit back in the car like it was in 2nd gear altho it was in neutral.You could still select all gears altho quit rough without engine running.Once the car is running you cant sellect any gear at all unless u turn engine off,put it in gear then re start engine,release clutch the car moves as normal but still cant get a gear with engine running.Hes checked clutch fork and bearing and there located as they should be,got a good clutch peddle so was wondering could this be down 2 the selecter not being correct?? Any help would be appreciated Lee