Manual (Steptronic) Mode Manual mode allows the transmission to operate as a semiautomatic 'Steptronic' unit. The driver can change up and down the five forward gears with the freedom of a manual transmission. Shift maps are provided for manual mode to protect the engine at high engine speeds. The EAT ECU will automatically change up to a higher gear ratio to prevent engine overspeed and change down to a lower gear ratio to avoid engine labouring and stalling. When kickdown is requested the EAT ECU downshifts at least 2 gears. When the vehicle is stationary, to drive off the driver can select st gear in high range, or st, 2nd or rd gear in low range. Any other gear selection will be rejected by the EAT ECU. When driving off, upshifts can be pre-selected by making + selections with the selector lever for the number of upshifts required. The EAT ECU then automatically performs a corresponding number of upshifts when the appropriate shift points are reached. So, for example, when starting off inst gear, if three + selections are made in quick succession, the EAT ECU will automatically change up through the box to 4th gear as the vehicle accelerates, without any further selections being made. In manual mode a low gear can be selected to provide engine braking for descending a slope without HDC or continuous use of the brake pedal. The driver can prepare for the end of the descent by moving the selector lever to D. The EAT ECU will maintain the low gear and only revert to automatic shift control when the throttle is opened and vehicle speed increases.
AUTOMATIC TRANSMISSION – ZF 5HP24 DESCRIPTION AND OPERATION 44-2-51