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Automatic Transmission

GM’s 2MT70

In the June 2010 issue of Transmission Digest we left off looking at the 2MT70 with having gone as far as removing the valve body. Getting back to this unit to have a brief look at the inside of it, with the rear covered removed the drive motor/generator assembly unit B becomes immediately visible (Figure 1). Inside the cover are the fourth clutch and the generator-position sensor.

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GM’s 2MT70

Technically Speaking

Subject: Internal components and operation
Unit: GM 2MT70
Vehicle Application: 2009 Saturn Vue 2.4-liter
Essential Reading: Rebuilder, Diagnostician
Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor

Part 2

Technically Speaking

  • Subject: Internal components and operation
  • Unit: GM 2MT70
  • Vehicle Application: 2009 Saturn Vue 2.4-liter
  • Essential Reading: Rebuilder, Diagnostician
  • Author: Wayne Colonna, ATSG, Transmission Digest Technical Editor

Part 2

In the June 2010 issue of Transmission Digest we left off looking at the 2MT70 with having gone as far as removing the valve body. Getting back to this unit to have a brief look at the inside of it, with the rear covered removed the drive motor/generator assembly unit B becomes immediately visible (Figure 1). Inside the cover are the fourth clutch and the generator-position sensor.

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Around the outside of both the drive-motor/generator assembly units A and B is a tube assembly used to cool these motor/generators as shown with generator assembly unit B in both figures 2 and 3.

A torque-damper assembly is used in this transmission instead of a conventional torque converter. This damper assembly contains both internal torsional springs and a clutch that acts as a spring coupling to smoothly transmit power from the engine to the transmission.

The clutch is applied only during engine starting and stopping events. Hydraulic pressure is used to control the application of the clutch via the damper-bypass clutch valve and pressure-control-solenoid 5 signal oil in the valve body. Pressure enters the assembly through the tip of the input shaft (Figure 4). The O-rings fitted to the input-shaft seal control exhaust pressure returning to the damper-bypass clutch valve where the application of the clutch is controlled.

When you split the case (Figure 5), many internal components come into view such as the drive-motor/generator assembly unit A, the auxiliary pump (used in EVT modes when engine is shut off), the 1-3 reverse-clutch assembly (figures 5 & 6) and the main fluid-pump-body assembly.

Since there are two pumps – the auxiliary pump and a gear crescent-style pump in the fluid-pump-body assembly (Figure 7) – there are also two internal filters (Figure 8).

Once the drive-motor/generator assembly unit A and the cooler-tube assembly are removed, the variable high and 2-3-4 clutch-drum assembly can be lifted out for service (Figure 9).

Inside the case you can see that the variable low & 1-2 reverse-clutch assembly needs to be unbolted so you can service it (Figure 10).

A simple special-tool package will prove to be quite helpful in disassembling a couple of these drum assemblies. It is part number DT 49098 from Kent-Moore, to be used for both the variable high and 2-3-4 clutch drum and 1-3 reverse clutch-drum assemblies. Without it, you could have a bit of a difficult time. The kit includes shim inserts and a two-piece snap-ring compressing device that clips onto the tips of a typical pair of pliers. The compressing device enables you to properly depress the snap ring. The shim inserts hold the snap ring in the compressed position, allowing you to easily remove the pressure-plate and clutch assembly from the drum.

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