jf1500

At last able to get into garage and take top off gearbox. Nothing obvious at first inspection. Removed overdrive and established problem not in overdrive. Closer inspection showed 4th gear synchro ring not free like others. Gentle levering managed to move synchro hub to permit careful work with small screwdriver and synchro ring popped free of synchro hub. Now rattles like the others and shafts move freely. Plan to replace top and gear change to see if it remains free after operating gearchange a few times. Hope it was just caused by not being used for about 25 years.

Thanks for your replies, gives me good indication where to start looking. Box hasn't been used for +20 years so will take top off as soon as I can get the box out (short of garage space) and run through your suggestions. Will let you know what I find.

In neutral gearbox input shaft turns freely but the overdrive output turns with it. Restrain the output and I can only just turn the input by slipping the clutch plate on it. Any ideas what could be causing this?