Transmission Component and System Description

1999 GMC Forward Control 5.7 R, AutomaticSECTION Transmission Component and System Description
WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. However, it is still accessible from the selected car via links, so may be relevant.

The mechanical components of this unit are as follows:

  • A torque converter with an electronically controlled capacity clutch (ECCC)

    This transmission is equipped with an electronically controlled capacity clutch (ECCC). The pressure plate does not fully lock to the torque converter cover. Instead, the pressure plate maintains a small amount of slippage, about 20 RPM, in SECOND, THIRD and FOURTH gears, depending on the vehicle application. ECCC was developed to reduce the possibility of noise, vibration or chuggle caused by TCC apply. Typical apply speeds are 49-52 km/h (30-32 mph) in THIRD gear and 65-73 km/h (40-45 mph) in FOURTH gear. Full lockup is available at highway speeds on some applications.

  • A drive link assembly
  • 4 multiple disk clutch assemblies: Input, Second, Third and Fourth
  • 3 friction bands: Forward band, 2/1 band and Reverse band
  • 2 planetary gear sets: Input and Reaction
  • 3 one-way clutches: a roller clutch (1-2 support) and 2 sprag clutches (Third and Input)
  • A final drive and differential assembly
  • A control valve assembly
  • A vane type oil pump

The electrical components of this unit are as follows:

  • 2 shift solenoid valves
  • A torque converter clutch pulse width modulation (TCC PWM) solenoid valve
  • A pressure control (PC) solenoid valve
  • An automatic transmission fluid temperature (TFT) sensor
  • 2 speed sensors: input shaft and vehicle speed sensors
  • An automatic transmission fluid pressure (TFP) manual valve position switch
  • Either an internal mode switch (IMS) or an externally-mounted transmission range (TR) switch.
  • An automatic transmission (A/T) wiring harness assembly

For more information, refer to Electronic Component DescriptionΒ .

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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

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