A drivetrain for an agricultural vehicle comprising: first and second driven axles; a variable pivot angle hydraulic motor connectable to drive the first axle by engagement of a first clutch mechanism; a further motor connected to drive the second axle; characterised in that there is provided: a controller having an input to receive an indication of a variable vehicle parameter value and being configured to control: the pivot angle (β) of the variable pivot angle hydraulic motor such that the angle decreases with variation of the vehicle parameter value to a point at which the pivot angle reaches zero at a first parameter value; engagement and disengagement of the first clutch mechanism including, with the pivot angle (β) at zero and vehicle parameter value continuing to vary due to the drive of the further motor, disengaging the first clutch mechanism at a second vehicle parameter value; wherein the first and second vehicle parameter values are separated by an interval determined at least partly by an operating characteristic of the first clutch mechanism. first and second driven axles; a variable pivot angle hydraulic motor connectable to drive the first axle by engagement of a first clutch mechanism; a further motor connected to drive the second axle; characterised in that there is provided: a controller having an input to receive an indication of a variable vehicle parameter value and being configured to control: the pivot angle (β) of the variable pivot angle hydraulic motor such that the angle decreases with variation of the vehicle parameter value to a point at which the pivot angle reaches zero at a first parameter value; engagement and disengagement of the first clutch mechanism including, with the pivot angle (β) at zero and vehicle parameter value continuing to vary due to the drive of the further motor, disengaging the first clutch mechanism at a second vehicle parameter value; wherein the first and second vehicle parameter values are separated by an interval determined at least partly by an operating characteristic of the first clutch mechanism. a controller having an input to receive an indication of a variable vehicle parameter value and being configured to control: the pivot angle (β) of the variable pivot angle hydraulic motor such that the angle decreases with variation of the vehicle parameter value to a point at which the pivot angle reaches zero at a first parameter value; engagement and disengagement of the first clutch mechanism including, with the pivot angle (β) at zero and vehicle parameter value continuing to vary due to the drive of the further motor, disengaging the first clutch mechanism at a second vehicle parameter value; the pivot angle (β) of the variable pivot angle hydraulic motor such that the angle decreases with variation of the vehicle parameter value to a point at which the pivot angle reaches zero at a first parameter value; engagement and disengagement of the first clutch mechanism including, with the pivot angle (β) at zero and vehicle parameter value continuing to vary due to the drive of the further motor, disengaging the first clutch mechanism at a second vehicle parameter value; wherein the first and second vehicle parameter values are separated by an interval determined at least partly by an operating characteristic of the first clutch mechanism.