The difference in gearboxes for X1 derivatives is due to engine torque application. The 4 wheel drive models use the Toyota sourced Aisin 8 Speed auto which is a conventional auto gearbox with no torque converter, hence experiencing the ‘lumpiness’ at low engine speed. This ‘lumpiness’ can also be experienced and attributed due to driving mode chosen. The Eco Pro mode is predominately for motorway or long uninterupted journeys as its main attribute is to save fuel, which it does by using a ‘coasting’ function and a softer ‘laggy’ throttle response, which can sometimes be experienced when pressing the accelerator when a sudden burst of speed is required. The default driving mode is ‘Normal’ which is as it states is ‘normal’ for general everyday town driving. I have found this mode to be more attentive for everyday use with better throttle response at road junctions and traffic lights, although the drive can sometimes be quite ‘aggressive’ if the accelerator is pressed harshly when slowly moving or when in a high gear. Sport mode is self explanatory, being for times of rapid acceleration with the gearbox holding onto gears much longer in the rev range for greater acceleration to attain rapid higher speeds.
The ‘lumpiness’ can also be the result of different people driving the car as the gearbox has a ‘learning’ memory function which attempts to map out the driving style of the driver, which sometimes results in a miscalculation. I have had the software reset several times on my X1 for the reasons of unanticipated drive characteristics only for the the issue to be resolved and then return some weeks later as my wife also drives my X1 of whom has a different driving style to myself.
The 7 speed gearbox as fitted to the 2 wheel drive X1 is a twin clutch DSG type unit made under licence for BMW by Steyer in Austria. This gearbox is mated to the lesser torque engines and again has no torque converter. I have no experience of driving any BMW with this engine so cannot comment of its driving characteristics.
The premium gearbox is the ZF 8 speed auto as fitted to the premium BMW ranges which of those who have experienced these ZF gearboxes you will know how refined they are, with no lumpiness, lag, jerkiness or snatching of gears which is due to the application of the torque converter which acts as a shock absorber in reducing and refining high inertia power to produce smooth gear changes.