knocking gearbox/axle

[Neil king]

can anyone tell me what would be knocking in gearbox or axle on a jcb 3c2 only seems bad in 4 th and 5 th in high box not tried in low ?
sounds like someone in there with a hammer can hear it one 3rd but not as noticeable

[essexpete]

Can you jack up the machine and run in gear slowly to pin point the area? Be careful, you might go from repairable to completely fffuked.

[MrF]

The whole top cover of the box comes off along with the gearchange mechanism and shift forks etc, and you can see into the top of the gear cluster for a better view too.
I have one of those mk2 boxes on a pallet, but as I'm in France it'd be cheaper for you to buy a replacement 3c2 than to ship it currently.