A gas turbine engine assembly comprising: a first spool having a first turbine operatively mounted to a first turbine shaft; a second spool having a second turbine operatively mounted to a second turbine shaft, the first and second turbines (54,46) mounted for rotation about a common rotational axis within an engine static structure, the first and second turbine shafts (50,40) coaxial with one another; first and second towershafts (64,66) respectively coupled to the first and second turbine shafts (50,40); an accessory drive gearbox with a set of gears; a starter generator assembly; a first clutch disposed between the first towershaft and the starter generator assembly, the first clutch configured to enable the starter generator assembly to drive the first spool through the accessory drive gearbox; a second clutch disposed between the second towershaft and the starter generator assembly, the second clutch configured to enable the second spool to drive the starter generator assembly through the accessory drive gearbox; and a transmission coupling the starter generator assembly to the set of gears, the transmission transitionable between a first mode where the starter generator assembly is driven at a first speed relative to the second towershaft, and a second mode where the starter generator assembly is driven at a different, second speed relative to the second towershaft, characterised in that: the gas turbine engine assembly further comprises an oil pump selectively driven by the second towershaft, wherein the starter generator assembly is driven by the second towershaft at a first speed relative to the oil pump when the transmission is in the first mode, and the starter generator assembly is driven by the second towershaft at a different, second speed relative to the oil pump when the transmission is in the second mode. a first spool having a first turbine operatively mounted to a first turbine shaft; a second spool having a second turbine operatively mounted to a second turbine shaft, the first and second turbines (54,46) mounted for rotation about a common rotational axis within an engine static structure, the first and second turbine shafts (50,40) coaxial with one another; first and second towershafts (64,66) respectively coupled to the first and second turbine shafts (50,40); an accessory drive gearbox with a set of gears; a starter generator assembly; a first clutch disposed between the first towershaft and the starter generator assembly, the first clutch configured to enable the starter generator assembly to drive the first spool through the accessory drive gearbox; a second clutch disposed between the second towershaft and the starter generator assembly, the second clutch configured to enable the second spool to drive the starter generator assembly through the accessory drive gearbox; and a transmission coupling the starter generator assembly to the set of gears, the transmission transitionable between a first mode where the starter generator assembly is driven at a first speed relative to the second towershaft, and a second mode where the starter generator assembly is driven at a different, second speed relative to the second towershaft, characterised in that: the gas turbine engine assembly further comprises an oil pump selectively driven by the second towershaft, wherein the starter generator assembly is driven by the second towershaft at a first speed relative to the oil pump when the transmission is in the first mode, and the starter generator assembly is driven by the second towershaft at a different, second speed relative to the oil pump when the transmission is in the second mode.