K 3500 Truck 4WD V8-5.7L VIN R (1998)
Shift Solenoid: Description and Operation
4L60-E Automatic Transmission
1-2 AND 2-3 SHIFT SOLENOID VALVES
IMPORTANT: The shift solenoid valve resistance should measure 19 - 24 ohms minimum when measured at 20°C (68°F). The shift solenoid
current flow should not exceed 0.75 amps. The shift solenoid should energize at a voltage of 7.5 volts or more (measured across the terminals). The
shift solenoid should de-energize when the voltage is one volt or less.
If both solenoids lose power, third gear only results. 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 PCM 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.
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. Diagnostic trouble codes P0753 and P0758 indicate shift solenoid circuit voltage
faults.
The PCM-controlled shift solenoids eliminate the need for TV and governor pressures to control shift valve operation.
3-2 SHIFT SOLENOID VALVE ASSEMBLY
IMPORTANT: The 3-2 shift solenoid valve assembly resistance should be a minimum of 20-24 ohms at 20°C (68°F).
The 3-2 shift solenoid valve assembly is an ON/OFF solenoid 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.
If a voltage fault is detected in the 3-2 shift solenoid circuit, diagnostic trouble code P0785 will set.
