Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
(Gearshift System, Basic Function - GF27.60-P-1002A)
Transmission 700.420/421/422/423, 724.033/044/045/103/114/115/120
Overview
This document contains information on:
- General
- Function requirements
- Function
General
Combustion engines provide usable torque only in a limited RPM range. Therefore, the gear ratio is adapted to suit the desired vehicle speed using the gear selection.
The gear is selected electrically or electrohydraulically by means of the fully integrated transmission control electrohydraulic controller unit or the dual-clutch transmission control unit. The following gear selection options are available to the driver:
- DIRECT SELECT selector lever
- Steering wheel gearshift buttons (manual intervention)
- Automatic transmission transmission mode button
Function requirements
- Engine in operation
- Clutch of sub-transmission disengaged
Function
An actuator moves the shift fork of the respective sub-transmission along the fork bar. Linear movement of the shift fork moves the sliding sleeve connected to the shift fork, axially along the output shaft. The axial movement of the sliding sleeve initiates synchronization between the output shaft and the idler gear of the selected gear range.
After synchronization, the sliding sleeve is pushed by the shift fork onto the interlock teeth of the idler gear. A positive connection is then generated between the idler gear and the power output shaft via the synchronizer body.
The actuators of the corresponding shift forks can take the form of an actuator motor or regulation valve. In the case of the version with actuator motors, the gearshift linkages are actuated via selector drums.
| Function schematic | |||
| Function schematic for gearshift system | PE27.60-P-2500-97A | ||
| Additional basic functions | |||
| ECO start/stop, basic function | GF07.10-P-1051A | ||
| Synchronization, basic function | Transmission 700.420/421/422/423, 724.033/044/045/103/114/115/120 | GF27.10-P-1001A | |
| Further detailed information | |||
| Detailed information on gear ratio | Transmission 700.420/421/422/423, 724.033/044/045/103/114/115/120 in model 118, 177, 247 | GF27.10-P-1102A | |
| Gear recognition sensor, detailed information | Transmission 700.420/421/422/423 | GF27.19-P-2502A | |
| Even/odd gears actuator motor, detailed information | Transmission 700.420/421/422/423 | GF27.19-P-2503A |
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.