When you say gearbox, I assume you mean the drive case, lets call it
that.
Early ones had a chain and a pair of sprockets in there, later ones have
a
ribbed drive belt like a car's cam belt. What have you got?

Steve


Mine has 3 chains and various sprockets. I don't know how old the
mower is, but it looks pretty ancient. That said, the forward roller,
in front of the blades, is plastic


3 chains? All in the one case? I'd really like to see this, I'm confuzzled
now. Any chance of a pic on photobucket or whatever? Or email it to me at
shazzbat3ATyahooDOTcoDOTuk

Steve