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Fig. 554: Overdrive Range, 4-3 Downshift OVERDRIVE RANGE, 3-2 DOWNSHIFT Similar to a forced 4-3 downshift, a forced 3-2 downshift can occur because of minimum throttle Energized by the PCM, the normally open solenoid closes and blocks the signal B fluid from 2-3 Shift Valve Train The signal B fluid pressure from the shift solenoid moves both valves to the downshift position The AFL fluid is blocked from the D432 fluid circuit and the D432 fluid exhausts past the The 2nd fluid is blocked from feeding the 3-4 signal fluid circuit and the 2nd fluid is routed
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The 3-4 signal fluid is exhausted past the valve. The 3-4 clutch fluid and the 3rd 3-4 Clutch Releases and 2-4 Band Applies 3-4 Clutch Piston The 3-4 clutch fluid exhausts from the piston and the 3-4 clutch plates are released. 3-4 Clutch Exhaust Checkball (#4) Exhausting 3-4 clutch fluid seats the #4 checkball and is forced through orifice #13. This orifice 2-4 Servo Assembly The 3rd accumulator fluid exhausts from the servo assembly. The 2nd clutch fluid pressure moves 3-2 Downshift Valve and 1-2 Upshift Checkball (#8) The 3-4 clutch fluid exhausts from the valve and the spring force moves the valve into the second Downshift Timing and Control At higher vehicle speeds, the 2-4 band apply must be delayed to allow the engine speed RPM to 3rd Accumulator Checkball (#2) The exhausting 3rd accumulator fluid seats the #2 checkball and is forced through orifice #12.
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
3-2 Control Solenoid Valve and 3-2 Control Valve These components are used to increase the exhaust rate of 3rd accumulator fluid, as needed, The 3-2 control solenoid valve is a normally closed On/Off solenoid controlled by the PCM. The Low Speed At lower vehicle speeds, the PCM operates the 3-2 control solenoid valve in the Off In the Off position the solenoid blocks actuator feed limit fluid pressure from the 3-2 With no actuator feed limit fluid pressure, the 3-2 control valve spring force keeps the valve A faster exhaust of the 3rd accumulator exhaust fluid provides a faster apply of the 2-4 High Speed At high vehicle speed, the PCM operates the 3-2 control solenoid valve in the On position This action permits a slow apply of the 2-4 band by blocking off 3rd accumulator exhaust This allows the engine speed to easily come up to the necessary RPM before the 2-4 band is 3rd Accumulator Exhaust Checkball (#7) After the downshift is completed, the #7 checkball unseats and allows the residual fluid in the 3rd Pressure Control (PC) Solenoid Valve Remember that the PC solenoid valve continually adjusts torque signal fluid in relation to the
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Fig. 555: Overdrive Range, 3-2 Downshift MANUAL THIRD GEAR A manual 4-3 downshift is available to increase vehicle performance when the use of only three Manual Valve The selector lever moves the manual shaft and manual valve into the Manual Third position (D). Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly D3 fluid is routed to the TFP manual valve position switch and opens the normally closed D3
2008 Chevrolet Silverado 1500 2008 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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