The automatic transmission gear shift moments are controlled by an electro-hydraulic system (so-called EN·management). This means that the hydraulic system of the gearbox is controlled by an electronic control unit, which, depending on the speed and engine load, selects the correct shift points.
To better suit the gear selection to the driver's individual driving style and driving conditions, the automatic transmission is equipped with an adaptive control system (AGS). It takes into account various conditions when selecting gears, such as driving in the mountains, towing a trailer, driving on slippery roads or driving in city mode (frequent stops) as well as the driver's driving style. The AGS system analyzes the position and movement of the accelerator pedal, the driving speed, lateral acceleration (cornering) and slowing down on turns.
Based on this information, the system determines the driving style and enters it into one of four preset basic programs. These basic programs range from the particularly economical XE program via the E and S programs to the XS sports program. A driver with a sporty driving style can, if necessary, switch on the "hard" sports program using position 4 of the selector lever. On slippery roads, an additional "winter" program is automatically switched on to increase driving stability.
Automatic transmission components ZF4HP22
1 — secondary shaft flange;
2 - screw cap;
3 - oil pan with control device;
4 — shift control lever shaft;
5 — gas drive cable;
6 - air bleed from the box;
7 - parking lock gear;
8 - centrifugal regulator;
9 - planetary gear;
10 - lamella (viscous) clutch;
11 - oil pump;
12 - torque converter;
13 — converter locking clutch;
14 — slave disk connection.
STEPTRONIC — automatic transmission with AGS and step-by-step gear shifting
Some models with the STEPTRONIC system have a second short channel (linkage) with the ability to change gears stepwise next to the main channel for the selector. Stepwise gear shifting is common on motorcycles, especially sports ones.
In the automatic mode, which is engaged for forward movement in the D range, the automatic 5-speed gearshifts are usually carried out using the Adaptive Gear Shift Control (AGS) system. When the lever is in the left shifter, on the contrary, the driver can select gears at will. If he moves the selector lever in the left shifter (channel) from the D position to the M position, the previous gear is maintained. If the driver moves the selector lever forward in the "+" direction, the transmission shifts to the next higher gear, and if in the "-" direction, to the next lower gear.
Unlike manual shifting, the STEPTRONIC system ensures comfortable driving and eliminates erroneous commands: the system ignores impermissible shifts, such as downshifting at very high revs. When accelerating with the KICKDOWN system in operation, (forced downshifting when the gas pedal is pressed sharply) without the selector being activated, a downshift to the lowest possible gear is mandatory. When accelerating without manual intervention, the system switches the gearbox to a higher gear when the engine speed is slightly below the maximum value.
When coasting, STEPTRONIC automatically downshifts to third gear to ensure sufficient traction when towing a trailer.
To check the operation of the automatic transmission and for correct diagnostics, we find experience working with automatic transmissions and special devices. Therefore, only the removal of the gearbox, adjustment of the gear shift cable and oil change are described here.
Automatic transmission shift levers ZF4HD22
1 - gear shift lever;
2 - lower part of the gearshift lever;
3 - support plate;
4 - gasket;
5 — wings;
6 - gear shift handle;
7 - push contact;
8 - switch;
9 — lever;
10 — shift rod;
11 - lower part of the gearshift lever;
12 — shift control shaft;
13 — gear selection disc;
14 - latch;
15 — cam;
16 — "kickdown" cable;
17 — mounting pin.