Our main drive gearbox on our 1640 keeps giving problems. We have just replaced the crown wheel for the second time in 3 seasons. Having spoken to other people the 1640_1440 gearboxes are known to be a problem. Therefor I figure how easy is it to fit a 1460_1660 gearbox to the chassis. I reckon it is constant wet weather work that causes the problems Cheers BB