am I right the gearbox is the bit where it goes 90o from the motor onto the main spindle? sorry I have never done mechanical stuff before, can do wood and building stuff but this is all new to me.
Yes there are some gears in the box between the motor and the extractor cage shaft. It might even be that the bearing has failed, so the gears don't mesh properly.
However, that doesn't look like a current product.
Which may make repair difficult to the point of being uneconomic.
I've no idea whether your motor (and cage-shaft) would fit onto a current-model gearbox.
However, ISTR that Park Beekeeping at Blackheath do offer a service of attaching a new motor (and gearbox) onto almost any extractor. Usually this can mean them making up an adaptor to go between the old extractor shaft and the shaft coming out of the new gearbox.
If you really don't have a clue about this stuff, you are going to have to trust a specialist of some sort or other.
It'd probably help to try and identify *where* the problem lies, even if you can't tell exactly what it is or how to fix it.
As I suggested previously, gently rotate the cage by hand, working it to and fro, feeling for any part of the rotation that doesn't feel the same.