Content .. 1172 1173 1174 1175 ..
Chevrolet Silverado / GMC Sierra. Manual - part 1174
Manual shift shaft switch status
1-2 and 2-3 Shift Solenoid Valves
Fig. 539: View Of 1-2 & 2-3 Shift Solenoid Valve
Courtesy of GENERAL MOTORS CORP.
The 1-2 and 2-3 shift solenoid valves (also called A and B solenoids) are identical devices that
control the movement of the 1-2 and 2-3 shift valves (the 3-4 shift valve is not directly controlled
by a shift solenoid). The solenoids are normally-open exhaust valves that work in four
combinations to shift the transmission into different gears.
The transmission control module (TCM) energizes each solenoid by grounding the solenoid
through an internal quad driver. This sends current through the coil winding in the solenoid and
moves the internal plunger out of the exhaust position. When ON, the solenoid redirects fluid to
move a shift valve.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
The TCM-controlled shift solenoids eliminate the need for TV and governor pressures to control
shift valve operation.
3-2 Shift Solenoid Valve Assembly
Fig. 540: View Of 3-2 Shift Solenoid Valve Assembly
Courtesy of GENERAL MOTORS CORP.
The 3-2 shift solenoid valve assembly is a normally-closed, 3-port, ON/OFF device that is used in
order to improve the 3-2 downshift. The solenoid regulates the release of the 3-4 clutch and the 2-
4 band apply.
Transmission Pressure Control Solenoid
IMPORTANT: The manual valve hydraulically can override the shift solenoids.
Only in D4 do the shift solenoid states totally determine what
gear the transmission is in. In the other manual valve positions,
the transmission shifts hydraulically and the shift solenoid states
CATCH UP when the throttle position and the vehicle speed fall
into the correct ranges.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
Fig. 541: View Of Transmission Pressure Control Solenoid
Courtesy of GENERAL MOTORS CORP.
The transmission pressure control solenoid is an electronic pressure regulator that controls
pressure based on the current flow through its coil winding. The magnetic field produced by the
coil moves the solenoid's internal valve which varies pressure to the pressure regulator valve.
The transmission control module (TCM) controls the pressure control solenoid by commanding
current between 0.1-1.1 amps. This changes the duty cycle of the solenoid, which can range
between 5-95 percent, typically less than 60 percent. High amperage (1.1 amps) corresponds to
minimum line pressure, and low amperage (0.1 amp) corresponds to maximum line pressure, if
the solenoid loses power, the transmission defaults to maximum line pressure.
The TCM commands the line pressure values, using inputs such as engine speed and throttle
position sensor voltage.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
The pressure control solenoid takes the place of the throttle valve or the vacuum modulator that
was used on past model transmissions.
Torque Converter Clutch Solenoid Valve
Fig. 542: View Of Torque Converter Clutch Solenoid Valve
Courtesy of GENERAL MOTORS CORP.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis
Silverado, Sierra & Silverado
Content .. 1172 1173 1174 1175 ..