|21 Nov 2017 05:10 PM
The Mercedes-Benz 722.6 (or NAG1 for Neue Automatikgetriebe 1) transmission is an electronically controlled gearbox mated to a lock-up clutch equipped torque converter. It first appeared in the mid-90s and has been in use on Mercedes-Benz passenger cars and vans ever since. Its’ variants also found their way into Jaguar, Porsche and Chrysler/Jeep/Dodge cars. Some of the transmission variants can handle up to 900 Nm of torque ex-works.
I have managed to gather the following technical information for the variant 722.611 (W5A330) which is rated at 330 Nm of input torque:
1st Gear 3.93
2nd Gear 2.41
3rd Gear 1.49
4th Gear 1.00
5th Gear 0.83
Reverse Gear 1 -3.10
Reverse Gear 2 -1.90
The transmission bears a 13-pin electrical connector with which it is controlled. The wires are 0.8 mm in diameter (20 gauge). Pin 5 on the connector is not used, so there are 12 live contacts.
Early transmissions also had and extra output speed sensor (4-pin connector, 3 pins live) which was feeding the signal through a ballast to the Transmission Control Unit.
Signals provided by the transmission
2 RPM sensors (namely n2 and n3). They seem not to be measuring input / output speed directly. They rather measure internal transmission rotating components speed. They are both measuring on 60-teeth patters and they seem to be of hall-effect type sensors (the are internally wired with 3 wires). Sensor n2 provides its’ output to pin 3 whilst sensor n3 provides its’ output to pin 1. They are both grounded via pin 12 and are supplied with current via pin 7.
Oil temperature sensor (namely b1). It is a temperature dependent resistor connected to pins 4 (signal) and 12 (ground). It is connected in line with the starter lockout contact switch (see below). Temperature information is thus only available when the selector is not in ‘P’ or ‘N’. Sensor calibration data is available.
Starter Lockout Contact (namely s1). It is a switch which is connected in line with the temperature sensor. It is open (i.e. no current flows) when the selector lever is in ‘P’ or ‘N’ and closes in all other selector lever positions.
Output Speed Sensor (namely B49). Separate from the 13-pin connector. No further information available yet.
Actuators on the transmission
The transmission has 6 solenoid valves which control its’ hydraulic circuits.
Modulating pressure control solenoid valve (namely y1). Seems to be PWM controlled. It is connected to pin 6 (which is the common supply for all solenoids) and pin 2 (ground). It is controlled via pin 2.
Shift pressure control solenoid valve (namely y2). Seems to be PWM controlled. It is connected to pin 6 (supply) and pin 10 (ground). It is controlled via pin 10.
1-2 and 4-5 shift solenoid valve (namely y3). Seems to be on/off controlled. It is connected to pin 6 (supply) and pin 13 (ground). It is controlled via pin 13.
3-4 shift solenoid valve (namely y4). Seems to be on/off controlled. It is connected to pin 6 (supply) and pin 11 (ground). It is controlled via pin 11.
2-3 shift solenoid valve (namely y5). Seems to be on/off controlled. It is connected to pin 6 (supply) and pin 8 (ground). It is controlled via pin 8.
Torque converter lockup PWM solenoid valve (namely y6). It is PWM controlled. It is connected to pin 6 (supply) and pin 9 (ground). It is controlled via pin 9.
Latest models are equipped with a touch-shift selector lever (P-R-N-D and ‘+’ & ‘-‘) with mechanical linkage for P-R-N-D and which provides signals via CAN bus for upshift/downshift.
Earlier models (like the first ML-Class) equipped with the 722.6 transmission were fitted with a voltage coded selector lever (P-R-N-D-4-3-2-1) with mechanical linkage for P-R-N-D and voltage output via a Gear Recognition Switch. No further information yet.
I am planning to do a logging/analysis of the actual electrical signals between the transmission and the transmission control unit in the next couple of weeks.
I will post the results here as soon as they are available.
From my point of view there are is a fundamental difference with the other transmissions currently supported by MegaShift. The difference lies in the presence of two pressure controlling solenoids instead of one.
I know that the basic design of the 722.6 family of transmissions has remained the same over the years. Of course lots of technical improvements have been introduced.
I presume that once MegaShift is configured to run the particular transmission, any other 722.6 transmission will be just a matter of tuning.
I would like to hear you comments and opinions on the subject.
Regarding the two pressure regulating solenoids I have some more information:
Shift pressure control solenoid valve (y2) controls the shift pressure. Shift pressure varies depending on engine/transmission load and gear change.
Shift pressure regulates the pressure in the activating shift elements during the shift phase and determines (together with the modulating pressure) the pressure reduction at the deactivating shift elements.
Shift pressure also initiates 2nd gear in emergency (limp-home) mode.
Shift pressure ranges between 0 to 15 bar (0-220 psi).
Modulating pressure control solenoid valve (y1) controls the modulating pressure. Modulating pressure varies depending on engine/transmission load.
Modulating pressure influences the magnitude of the working pressure and determines (together with the shift pressure) the pressure reduction at the deactivating shift elements.
Modulating pressure ranges between 0 to 8 bar (0-120 psi).
The working pressure (or Line Pressure or Operating Pressure) provides the pressure supply to the hydraulic control and the transmission shift elements. It is the highest hydraulic pressure in the entire hydraulic system. The working pressure is regulated at the working pressure regulating valve in relation to the load and gear. All other pressures required for the transmission control are derived from the working pressure.
Working Pressure ranges between 3,5 to 24 bar (50-350 psi).
Regarding the transmission input shaft (turbine) speed, the combination of the two RPM sensors (n2 and n3) can bu used to obtain it: Depending on whether n3 is 0 or not, n2 output needs to be multiplied by a factor 'c' in order to obtain the real input shaft speed: Input Shaft Speed = n2 * If ( n3=0;c;1) -> (If n3 = 0 then input shaft speed equals n2 X c, otherwise input shaft speed = n2).
'c' is a constant and should be around 0,60.
When I have more information I will make them available.
Once again thanks.
|21 Nov 2017 05:27 PM
The Modulating pressure control solenoid valve (y1) is PWM controlled with a frequency of 1000Hz and a voltage magnitude of 12 volts. The duty cycle was found to be in the range of 40% to 60% and varied according to load. The higher the load the lower the duty cycle. I did not test the full spectrum of loads so maybe the overall range may vary.
The Shift pressure control solenoid valve (y2) is PWM controlled with a frequency of 1000Hz and a voltage magnitude of 12 volts. The particular solenoid is ONLY ACTIVE DURING SHIFTS. I measured a duty cycle of about 45% for the duration of the shift and then activity stops. It seems that this solenoid initiates and finalizes the shift phase of all shifts. One other interesting finding is that the solenoid is also active when the selector is in P or N. Maybe this is related to the emergency limp-home mode functionality.
The 1-2 and 4-5 shift solenoid valve (y3), 3-4 shift solenoid valve (y4) and 2-3 shift solenoid valve (y5) might also be PWM controlled, but I haven't thoroughly tested this. The are only active during the respective shifts. I measured a voltage of about 4.5 Volts during shifts. I was not able to check the timing of the activation in relation to the shift pressure solenoid because I did not have an osciloscope on the move.
The following table is a preliminary overview of the shift logic:
Engaged Gear, Shift Solenoid Enabled, Resulting Gear
1 y3 2
2 y3 1
2 y5 3
3 y5 2
3 y4 4
4 y4 3
4 y3 5
5 y3 4
I will thoroughly verify the validity of the table and post my findings.
Torque converter lockup PWM solenoid valve (y6) is PWM controlled with a frequency of 100Hz and a voltage magnitude of 12 volts. No further data could be gathered due to traffic related constraints.
Conclusively, shift pressure solenoid and shift solenoids are only active during shifts. The transmission cannot skip gears during shifts (i.e. It cannot go from 2nd to 4th directly. It will go from 2nd to 3rd and then from 3rd to 4th).
Further tests and results will follow.