Converter Update for GM's 4T80E Lowers Cost Without Harsh Apply

Introduction: The Cost of Transmission Repair

Cost is a significant factor in transmission repair. A common customer question upon learning a transmission rebuild is necessary is "how much?" This was particularly true for GM's 4T80E transmission.

The original 4T80E featured a Viscous Converter Clutch (VCC). The VCC utilizes a layer of silicone fluid between the converter cover and body to provide a smooth converter clutch apply. While this resulted in a barely noticeable, smooth engagement for the driver, replacing a VCC converter was expensive. Because VCC units are not rebuildable, a new one could cost over $500.

To offer a lower-cost alternative, many shops would switch customers to a standard, on/off converter clutch and block the TCC regulator valve. This reduced the cost significantly. However, the transmission's feel changed, with the converter clutch apply feeling like an additional shift, akin to a fifth gear. Customers were often displeased with this change, but it was a trade-off for the lower price, or they had to pay for the expensive VCC.

Textual description of Figure 1A: A diagram illustrating the Viscous Converter Clutch (VCC) assembly, showing components like the rotor, cover, body, and seals. It indicates the silicone fluid layer.

Understanding the Viscous Converter Clutch (VCC)

The VCC seals a layer of silicone fluid between the converter cover and body, which softens the converter clutch apply. This mechanism provides a smooth engagement that is difficult for the driver to perceive.

Textual description of Figure 1B: A cross-sectional diagram of the Viscous Converter Clutch (VCC), detailing the internal components and the silicone fluid layer between the converter cover and body, which softens the clutch apply. It shows a square cut seal and a double lip seal with a garter spring.

The friction material used on the VCC models is a standard paper type.

Textual description of Figure 1C: A close-up photograph of a transmission converter clutch component, showing the friction material on the surface.

The EC3 Update: A Cost-Effective Solution

In mid-2005, GM phased out the VCC system in favor of the EC3 system (Electronic Converter Clutch Control). The EC3 system had been in use in other applications since the mid-1990s. The EC3 converter clutch utilizes a woven carbon fiber material attached to the pressure plate. This carbon fiber material is designed for a high slip application, ensuring a smooth clutch apply, much smoother than a standard TCC.

The significant advantage is that earlier 4T80E transaxles can be updated to use the EC3 converter. This process is not overly difficult and results in a smooth clutch apply, very similar to the feel of the VCC. Crucially, the cost is considerably lower than the VCC, leading to customer satisfaction with both the transmission's operation and the rebuild price – a win-win situation.

Textual description of Figure 2: A close-up photograph showing the friction material used on the EC3 converter clutch, described as a woven carbon fiber material attached to the pressure plate.

Textual description of Figure 3: Diagrams comparing the "present design" and "new design" of a spacer plate for the transmission case cover. The new design includes an "Identification Hole" and shows differences in orifice configurations.

Components Required for the EC3 Update

The update to an EC3 system is designed for 4T80Es that were originally equipped with either the VCC or TCC. Several other changes are necessary to accommodate the new converter. These updated parts cannot be intermixed with earlier components or systems, as doing so could lead to problems with system operation or durability.

The EC3 update includes:

• A new EC3 torque converter (VCC converters may still be available for some applications).
• Updated computer calibration.
• A new case cover spacer plate (as shown in Figure 3).

Textual description of Figure 4: Diagrams comparing the "Current Design" and "New Design" of a spacer plate to case cover gasket, highlighting differences in orifice placement and size.

Textual description of Figure 5: Diagrams comparing the "Current Design" and "New Design" of a valve body to spacer plate gasket, showing changes in orifice configurations.

Updated Computer Calibration

The vehicle's computer will require a calibration update to properly manage the new converter clutch operation. These changes will adjust parameters for setting four Diagnostic Trouble Codes (DTCs): P0741, P0742, P2763, and P2764. This effectively eliminates the parameter window where the VCC would typically slip.

Updated Case Cover Spacer Plate and Gasket

The new spacer plate is designed to service both VCC and TCC applications. An ID hole has been added to the left corner of the new gasket for easy identification.

• For VCC applications, four orifice dimensions were changed.
• For TCC applications, three orifice dimensions were changed.

The updated spacer plate will be available in a kit, specifically for this modification. One passage change was required for the EC3 application gasket. The updated gasket is included in the service kit for updating prior VCC applications.

The updated gasket is included in the service kit to update prior VCC applications.

Converter Clutch Control Valve and TCC Enable Springs

An updated converter clutch control valve spring and TCC enable spring are required for the EC3 update. Both valves now utilize the same spring. The update kit is available under specific part numbers:

• 24233678 – For some TCC applications, including export models.
• 24233679 – For VCC applications.
• Alternatively, check with your aftermarket supplier.

This modification offers a significant benefit: the new converter provides an apply feel very similar to the original VCC converter, but at a fraction of the cost. Furthermore, the new EC3 is engineered for greater durability than the original VCC converter.

It is uncommon to find modifications that simultaneously improve durability and reduce cost. Given that cost is a major concern for customers, this update is excellent news for both technicians and their clients. The most critical aspect is ensuring the modification is performed completely and accurately to avoid potential driveability or diagnostic issues.

Textual description of Figure 6: Diagrams illustrating the "Current Design" and "New Design" of the valve body components related to the converter clutch control valve and TCC enable springs. It shows the components and their approximate free height measurements (28.19 mm for current, 38.56 mm for new).

Textual description of Figure 7: Photographs of two springs, labeled as the converter clutch control valve spring and TCC enable spring, showing their appearance.