Start Off And Stop, Basic Function - GF27.10-P-1004A

Transmission 700.420/421/422/423, 724.033/044/045/103/114/115/120 

Overview 

This document contains information on:

• General 
• Function requirements 
• Function 
  • Starting off the vehicle 
  • Stopping the vehicle 

General 

Vehicle standstill is the initial condition when starting off and the final state when the vehicle is stopped.

Function requirements 

• Drive train operational
• Engine in operation
• Transmission not in limp-home mode

Function 

The dual-clutch Transmission control unit or fully integrated Transmission control electrohydraulic controller unit detects whether and when the vehicle is at a standstill or is coming to a standstill. This is done by evaluating the following input signals:

• Engine speed
• Accelerator pedal position
• Wheel speeds of all wheels
• Service brakes operated

Starting off the vehicle 

Irrespective of the selected drive program, moving off takes place in 1st gear. In the Economy or Comfort drive programs, shifting to the next gear takes place at low engine speeds. This makes for an efficient driving style. In the Sport and Sport Plus Transmission modes, forced upshifts are made when close to the maximum governed rpm.

Stopping the vehicle 

If the vehicle speed is noticeably reduced, the dual-clutch Transmission control unit or the fully integrated Transmission control electrohydraulic controller unit automatically shifts back to the following drive programs:

• Individual (without selection of "Manual shift mode")
• Comfort
• ECO

The ideal gear is thereby engaged should acceleration be required.

In manual shift mode or in temporary drive program "M", a downshift is made close to the idle speed of the combustion engine. It is possible to shift down across several gears. If the vehicle comes to a standstill, shifting takes place in 1st gear.