Vehicle drivetrain modes

A control system for a vehicle drivetrain assembly, the control system comprising one or more controllers and the control system further comprising:

• i) an input means arranged to receive,
• a selection between a first mode and a second mode;
• a signal indicative of whether an automatic transmission of the vehicle drivetrain assembly is in first gear;
• and
• a signal indicative of whether a torque converter of the automatic transmission is stalled;
• ii) a processor arranged to determine a maximum torque limit for torque delivered to the transmission produced by a drive unit of the vehicle drivetrain assembly and when the automatic transmission is in the first gear with the torque converter stalled, the processor determines a maximum torque at a first level when the vehicle drivetrain assembly is in the first mode and determines a maximum torque at a second level when the vehicle drivetrain assembly is in the second mode, the first level being lower than the second level;
• iii) an output means arranged to send a signal to control torque delivery to the transmission in accordance with the determined torque limit.

A method of operating a vehicle drivetrain assembly where the vehicle drivetrain assembly comprises:

• a drive unit arranged to generate power to drive a vehicle;
• and
• an automatic transmission operatively coupled to the drive unit to receive the power, where the automatic transmission comprises a torque converter,
• the method comprising:
• when the automatic transmission is in first gear with the torque converter stalled, limiting a maximum torque delivered to the transmission from the drive unit to a first level when the vehicle drivetrain assembly is operating in a first mode and to a second level when the vehicle drivetrain assembly is in a second mode, the first level being lower than the second level.