The Direct Shift Gearbox Part 2 - Transmission Digest

The Direct Shift Gearbox Part 2

Housed inside the six-speed direct-shift gearbox (DSG) is a Mechatronics assembly consisting of a control module, valve body and solenoids (see figures 1 and 2). It is the control center that shifts this manual gearbox automatically by turning on and off two separate clutch drums called the K1 and K2 clutches.

The Direct Shift Gearbox Part 2

Technically Speaking

Subject: Operating principles
Unit: VW DSG 02E
Essential Reading: Rebuilder, Diagnostician
Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor

Technically Speaking

  • Subject: Operating principles
  • Unit: VW DSG 02E
  • Essential Reading: Rebuilder, Diagnostician
  • Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor

Housed inside the six-speed direct-shift gearbox (DSG) is a Mechatronics assembly consisting of a control module, valve body and solenoids (see figures 1 and 2). It is the control center that shifts this manual gearbox automatically by turning on and off two separate clutch drums called the K1 and K2 clutches.

Each clutch supplies engine torque to its respective input shaft, which then drives one of two output shafts. The K1 clutch and Input Shaft 1 provide 1st, 3rd, 5th and reverse gears, and the K2 clutch and Input Shaft 2 provide 2nd, 4th and 6th gears (see figures 3 and 4). As you can easily determine, K1 is cycled on for 1st and then turns off while K2 is cycled on for 2nd and so on.

The output-shaft configurations are slightly different from those of the input shafts in that Output Shaft 1 consists of 1st, 2nd, 3rd and 4th gears and Output Shaft 2 consists of 5th, Neutral, 6th and reverse gears (see figures 5 and 6).

Since the Mechatronics is control central, let’s begin by seeing all that it is equipped with to operate this cleverly designed unit, starting with the 11 solenoids shown in figures 7 and 8.

Each of the clutches (K1 and K2) has its own solenoid with which its assigned clutch is cycled on and off during gear changes, as you can see in the upper-left corner of Figure 8 (N215 for K1 and N216 for K2). Greater details of this solenoid and all the others, as well as other components integral to the Mechatronics, will be discussed in part 3 of this article.

The next four solenoids (N88, N89, N90 and N91) make up the shift-solenoid group. N88 is responsible for 1st and 5th gears, N89 takes care of 3rd and neutral, N90 handles 2nd and 6th, and N91 provides 4th and reverse.

For each of these shift solenoids to be able to provide two different gears at different times, a “multiplexer” valve in the valve body (see Figure 9) is operated by the multiplexer solenoid (N92), shown at the 3 o’clock position in Figure 8. The multiplexer solenoid turns on and off to stroke and un-stroke the multiplexer valve to redirect solenoid-signal pressure to the appropriate shift rail. The idea is similar to that of a Chrysler 604 (41TE) transmission, in which the solenoid shift valve in the valve body is stroked in such a way that it allows the L/R solenoid to double as a TCC solenoid.

Another interesting point is that this multiplexer solenoid is exactly like the one used as a converter-clutch solenoid in Saturn Vue continuously variable transmissions.

Volkswagen says that when the multiplexer solenoid is off, 1st, 3rd, 5th and reverse can be achieved, but from the hydraulics that I drew it seems that 1st, 3rd, 6th and reverse can be achieved. Conversely, VW says that when the solenoid is turned on, 2nd, 4th and 6th can be achieved, yet the hydraulics reveal that 2nd, 4th, 5th and neutral can be achieved (see Figures 10, 11, 12, 13, 14 and 15).

We now have four solenoids remaining. N217 is the main line-pressure-control solenoid, and N218 controls clutch cooling pressure. The other two are safety control solenoids. N233 controls the fluid circuit to the N215, N88 and N89 solenoids, and N371 controls the fluid circuit to N216, N90 and N91. These safety solenoids are used to isolate hydraulic pressure to its associated section of the gearbox. In other words, if a problem is detected with either 2nd, 4th, 6th or reverse, N371 shuts down pressure to N216, N90 and N91. 1st and 3rd will become failsafe gears. If a problem is detected in either 1st, 3rd or 5th, N233 shuts down pressure to N215, N88 and N89 and only 2nd gear will the failsafe gear.

When you compare the information provided in Figure 8 with the hydraulic schematics in figures 10 through 15, much of what we’ve explained will make a bit more sense, and we will continue with additional information on this unit next month.

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