A generator set comprising: an engine (110; 210) including a crankshaft; a generator (140; 240) including a generator shaft; a gearbox (120; 220) positioned between the engine and the generator and coupling the crankshaft to the generator shaft, wherein the gearbox (120; 220) comprises a gearbox housing (122; 222) and a gear set including a plurality of gears, a first gear shaft and a second gear shaft, the first gear shaft coupled to the crankshaft, and the second gear shaft coupled to the generator shaft; and a chassis (150; 250), each of the engine (110; 210), the gearbox housing (122; 222) and the generator (140; 240) positioned on and rigidly coupled to the chassis (150; 250); characterised in that: the gearbox housing (122; 222) has a first end (121; 221) directly coupled to the engine (110; 210) and a second end (125; 225) directly coupled to the generator (140; 240), the gearbox housing (122; 22) defining a continuous body connecting the first end (121; 221) and the second end (125; 225) so as to form an integrated torque bearing structure for transmission of torque load between the coupled elements of the engine, the gearbox and the generator; and the crankshaft, at least a portion of the plurality of gears, and the generator shaft are axially aligned when the gearbox is coupled to the engine and generator. an engine (110; 210) including a crankshaft; a generator (140; 240) including a generator shaft; a gearbox (120; 220) positioned between the engine and the generator and coupling the crankshaft to the generator shaft, wherein the gearbox (120; 220) comprises a gearbox housing (122; 222) and a gear set including a plurality of gears, a first gear shaft and a second gear shaft, the first gear shaft coupled to the crankshaft, and the second gear shaft coupled to the generator shaft; and a chassis (150; 250), each of the engine (110; 210), the gearbox housing (122; 222) and the generator (140; 240) positioned on and rigidly coupled to the chassis (150; 250); characterised in that: the gearbox housing (122; 222) has a first end (121; 221) directly coupled to the engine (110; 210) and a second end (125; 225) directly coupled to the generator (140; 240), the gearbox housing (122; 22) defining a continuous body connecting the first end (121; 221) and the second end (125; 225) so as to form an integrated torque bearing structure for transmission of torque load between the coupled elements of the engine, the gearbox and the generator; and the crankshaft, at least a portion of the plurality of gears, and the generator shaft are axially aligned when the gearbox is coupled to the engine and generator. the gearbox housing (122; 222) has a first end (121; 221) directly coupled to the engine (110; 210) and a second end (125; 225) directly coupled to the generator (140; 240), the gearbox housing (122; 22) defining a continuous body connecting the first end (121; 221) and the second end (125; 225) so as to form an integrated torque bearing structure for transmission of torque load between the coupled elements of the engine, the gearbox and the generator; and the crankshaft, at least a portion of the plurality of gears, and the generator shaft are axially aligned when the gearbox is coupled to the engine and generator.