ERAD, Gearbox
The gearbox is combined with the electric motor with a fixed gear consisting of gear wheel, pinion, crown wheel and differential.
The design can be likened to a manual gearbox with helical gears to minimize transmission noise. The gearbox is only used in situations when the electric motor is activated for propulsion or regeneration. The gearbox has no reverse gear. To reverse with activated electric operation, the electric motor's direction of rotation is changed. Maximum speed when reversing regardless of drive source is 30 km/h.
The gearbox is mounted in conical roller bearings at both ends and is sealed against the electric motor's input driving shaft with drive shaft seals. The left and right-hand drive shafts are connected to the differential by splines.
Specifications:
| Oil | Synthetic, specially developed transmission oil (Castrol BOT 448) |
| Oil volume | 550 ml |
| Gear ratios: | 10, 008:1 |
| Weight | 31 kg |
Power flow
Power is switched over from the electric motor's shaft to a larger gear on a parallel shaft in the gearbox. From this shaft the power continues via a gear to the crown wheel and the differential. On the right-hand side the power then flows from the differential via the drive shaft through the electric motor's hollow shaft to the rear wheel. On the left-hand side the power flows directly from the differential via the drive shaft to the rear wheel.
Gear shifter
The gear shifter in the Twin Engine is the "Shift by wire" type, and therefore fully electronic. There is no mechanical contact between the gear selector assembly and the gearbox. The driver's request for changed gear position is instead transmitted via a data bus.
The gear shifter has the following positions:
- P - Park
- R - Reverse
- N - Neutral
- D - Drive
- B - Brake
An electronic gear actuator is fitted on the gearbox and is connected to the gear selector mechanism. The function of the actuator is to mechanically select the requested gear position in the gearbox based on the control signal from TACM (Transmission Actuator Control Module). The actuator consists of an SR motor (Switched Reluctance motor) and a gear. The gear selector assembly's control module, EGSM, is fitted in the gear selector assembly.
Gear position B is new for the Twin Engine, and the B position is a variant of gear position D that adds extra strong engine braking via ERAD. The simulated engine braking is approximately twice as strong as "normal" simulated engine braking. This means it is particularly appropriate to use the B position while driving on hills or with a heavy trailer.
Differential
The differential distributes power equally between the drive wheels, even if they are rotating at different speeds. When driving straight ahead, the ring gear and differential housing rotate at the same speed as the drive shafts and the driving wheels. When cornering, the differential gears rotate to compensate for the different speeds of the wheels. Because the small differential gears are rotating on the shaft journal, the drive shafts can rotate at different speeds. Power is transferred from the differential housing to the drive shafts via the small differential gears in the same way as when driving straight ahead. Both drive wheels still have the same driven power.