Chevrolet Equinox Service Manual: Drive Range, First Gear Engine Braking (Gen 2/Hybrid) Automatic Transmission Unit

Note: Some models of the 6T30/40/45/50 automatic transmissionare equipped with an electric auxiliary fluid pump for use inhybrid vehicles (BAS+). Hybrid vehicles do not require internalcombustion engine (ICE) operation at all times. After a successfulengine start, the hybrid powertrain control module (HPCM) may turnOFF the engine (Auto Stop) when not required for the currentvehicle conditions. The engine will remain OFF while in Auto Stopmode, until such time that vehicle conditions require the engine torun. During Auto Stop mode the main fluid pump is no longer drivenby the engine, and the auxiliary fluid pump is commanded ON toprovide hydraulic fluid pressure to operate the transmission. Thisfunctional description of Drive Range– First Gear (EngineBraking), and its accompanying hydraulic circuit, is written for anon-hybrid transmission. For a hybrid (BAS+) transmission, thedescription and illustration are the same, with the exception that,when the engine is OFF, the main fluid pump is not operating andthe auxiliary fluid pump is ON.

When the gear selector lever is moved to the Drive (D) rangefrom the Neutral (N) position, the transmission will provide enginebraking. In this operating range, the normally-high 1234 pressurecontrol solenoid is commanded ON and, in the engine braking mode,the following changes occur within the hydraulic circuits.

1-2-3-4 Clutch Applies

Manual Valve

The manual valve is moved to the Drive (D) position andallows line fluid pressure to enter the drive fluid circuit. Drivefluid is then routed to the clutch select valve, the #5 ball checkvalve, and to the 2-6 clutch regulator valve.

#5 Ball Check Valve

Drive fluid unseats the #5 ball check valve and is routed tothe 1-2-3-4 clutch regulator valve.

1234 Pressure Control (PC) Solenoid

The 1234 PC solenoid is commanded ON allowing actuator feedlimit fluid to enter the PCS 1234 clutch fluid circuit. PCS 1234clutch fluid is then routed through orifice #20 to the 1-2-3-4clutch regulator valve, and through orifice #17 to the 1-2-3-4clutch boost valve.

1-2-3-4 Clutch Regulator Valve

PCS 1234 clutch fluid, at the 1-2-3-4 clutch regulator valve,opposes 1-2-3-4 clutch regulator valve spring force and 1234 clutchfeedback fluid pressure to regulate drive fluid pressure into the1234 clutch fluid circuit. The 1234 clutch fluid is then routed tothe 1-2-3-4 clutch boost valve and through orifice #19 to the1-2-3-4 clutch.

1-2-3-4 Clutch Boost Valve

PCS 1234 clutch fluid pressure acts on a differential area,moving the 1-2-3-4 clutch boost valve against 1-2-3-4 clutch boostvalve spring force, to regulate 1234 clutch fluid into the 1234clutch feedback circuit. As PCS 1234 clutch fluid pressure isincreased to a given value, the 1-2-3-4 clutch boost valve opensthe 1234 clutch feedback circuit to exhaust backfill. This resultsin the 1-2-3-4 clutch regulator valve moving to the full feedposition, sending full 1234 clutch feed pressure (full linepressure) to the 1-2-3-4 clutch.

1-2-3-4 Clutch

The 1234 clutch fluid enters the transmission case assemblyand moves the 1-2-3-4 clutch piston against spring force to applythe 1-2-3-4 clutch plates.

Accumulator

PCS 1234 clutch fluid is also routed to an accumulator valve.The accumulator valve is used to dampen any pressure irregularitiesoccurring in the PCS 1234 clutch fluid circuit. This helps tocontrol clutch apply fluid pressure and clutch apply feel.

Low and Reverse Clutch Remains Applied to Provide EngineBraking

Clutch Select Valve

Shift solenoid fluid, present at the valve from Parkposition, continues to hold the clutch select valve against clutchselect valve spring force. R1/456 clutch feed fluid, also presentat the valve from Park position, continues to pass into the R1circuit to feed the low and reverse clutch. Drive fluid is presentat the valve in preparation for a change of gears.

Low and Reverse Clutch

The low and reverse clutch remains applied until just beforethe 1-2 shift in order to provide engine braking.

Drive Range, First Gear EngineBraking-–-Gen 2/Hybrid

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