NEUTRAL – ENGINE RUNNING

When the gear selector lever is moved to the Neutral position (N) from the Reverse position, the following changes occur to the transmission hydraulic and electrical systems.

Manual Valve

In the Neutral position, the manual valve blocks the line pressure from entering any other fluid circuits. Reverse and PR fluids exhaust past the manual valve.

Lo and Reverse Clutch Releases Lo and Reverse Clutch Piston

PR and Lo/reverse fluids exhaust from the piston, thereby releasing the lo and reverse clutch plates. Exhausting PR fluid unseats the lo and reverse clutch checkball (#10) for a quick exhaust.

Lo Overrun Valve

Spring force closes the valve when the PR fluid pressure exhausts. Lo/reverse fluid exhausts through the valve, into the Lo/1st fluid circuit, past the 1-2 shift valve, into the Lo fluid circuit and through an exhaust port at the manual valve.

Reverse Input Cutch Releases Reverse Input Clutch Piston

Reverse input fluid pressure exhausts from the piston, through the boost valve, past the #3 checkball and to the manual valve. With the reverse input fluid exhausted, the reverse input clutch plates are released and the transmission is in Neutral.

Reverse Abuse Valve

Reverse fluid pressure exhausts and spring force closes the valve.

Boost Valve

Reverse input fluid pressure exhausts and line pressure returns to the normal operating range as in the Park and Overdrive positions.

Reverse Input Checkball (#3)

Exhausting reverse input fluid unseats the ball for a quick exhaust through the reverse fluid circuit and past the manual valve.

Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly

IMPORTANT: In Park, Reverse and Neutral the shift solenoid valves are shown energized. This is the normal operating state when the vehicle is stationary or at low vehicle speeds. However, the PCM will change the shift solenoid valve states depending on the vehicle

2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3

speed. For example, if Neutral is selected when the transmission is operating in Second Gear, the shift solenoid valves will remain in a Second Gear state. However, with the manual valve blocking line pressure, the shift solenoid valve states do not affect transmission operation in Park, Reverse and Neutral.

Reverse input fluid exhausts from the TFP manual valve position switch. With no other fluid routed to it, the TFP manual valve position switch signals the PCM that the transmission is operating in either Park or Neutral.

NEUTRAL - ENGINE RUNNING

Courtesy of GENERAL MOTORS CORP.

OVERDRIVE RANGE, FIRST GEAR

When the gear selector lever is moved to the Overdrive position, from the neutral position, the following changes occur to the transmission's hydraulic and electrical systems:

Manual Valve

Line pressure flows through the manual valve and fills the D4 fluid circuit. All other fluid circuits remain empty with the manual valve in the Overdrive position.

Forward Clutch Accumulator Checkball (#12)

D4 fluid pressure seats the checkball and is orificed (#22) into the forward clutch feed fluid circuit. This orifice helps control the forward clutch apply rate.

Forward Clutch Accumulator Piston

Forward clutch feed fluid pressure moves the piston against spring force. This action absorbs some of the initial increase of forward clutch feed fluid pressure to cushion the forward clutch apply.

Forward Clutch Abuse Valve

D4 fluid pressure acts on the valve opposite of spring force. At engine speeds greater than idle,

D4 fluid pressure increases and moves the valve against spring force (as shown). D4 fluid can then quickly fill the forward clutch feed fluid circuit, thereby bypassing the control of orifice #22 and providing a faster apply of the forward clutch. Otherwise, with increased throttle opening and engine torque, the clutch may slip during apply.

Transmission Fluid Pressure (TFP) Manual Valve Position Switch Assembly

D4 fluid pressure is routed to the TFP manual valve position switch and closes the normally open D4 fluid pressure switch. This signals the PCM that the transmission is operating in Overdrive range.

1- 2 Shift Solenoid (SS) Valve

Energized (ON) as in Neutral, the normally open solenoid is closed and blocks signal A fluid from exhausting through the solenoid. This maintains pressure in the signal A fluid circuit.

2- 3 Shift Solenoid (SS) Valve

Energized (ON) as in Neutral, the normally open solenoid is closed and blocks signal B fluid from exhausting through the solenoid. This maintains signal B fluid pressure at the solenoid end of the 2-3 shift valve.

2- 3 Shift Valve Train

Signal B fluid pressure at the solenoid end of the 2-3 shift valve holds the valve train in the downshifted position against AFL fluid pressure acting on the 2-3 shift valve. In this position, the

2- 3 shuttle valve blocks AFL fluid from entering the D432 fluid circuit. The D432 fluid circuit is open to an exhaust port past the valve.

Signal A fluid pressure holds the valve in the downshifted position against spring force. In the First gear position, the valve blocks D4 fluid from entering the 2nd fluid circuit.

Accumulator Valve

Biased by torque signal fluid pressure, spring force and orificed accumulator fluid pressure at the end of the valve, the accumulator valve regulates D4 fluid into accumulator fluid pressure. Accumulator fluid is routed to both the 1-2 and 3-4 accumulator assemblies in preparation for the

1- 2 and 3-4 upshifts respectively.

Rear Lube

D4 fluid is routed through an orifice cup plug (#24) in the rear of the transmission case to feed the rear lube fluid circuit.

Pressure Control (PC) Solenoid Valve

Remember that the PC solenoid valve continually varies torque signal fluid pressure in relation to throttle position and vehicle operating conditions. This provides a precise control of line pressure.

3-2 Control Solenoid Valve

The PCM keeps the solenoid OFF in First gear and the normally closed solenoid blocks filtered AFL fluid from entering the 3-2 signal fluid circuit.

Torque Converter Clutch PWM Solenoid Valve

In first gear, at approximately 6 mph, the PCM operates the TCC PWM solenoid valve at approximately a 90 percent duty cycle. This opens the AFL fluid circuit, to fill the converter clutch signal fluid circuit through the #9 orifice and flows to the isolator valve. The CC signal fluid pressure, acting on the isolator valve, will move the regulated apply valve towards the closed position. Regulated line pressure is now routed into the regulated apply circuit and flows to the closed converter clutch valve and is blocked from entering the converter clutch apply circuit. Regulated apply fluid is routed through the #8 orifice to the front of the regulated apply valve and regulates the line pressure entering the regulated apply circuit, in response to the CC signal fluid acting on the isolator valve.

2007 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E/4L70-E - H3

NEUTRAL - ENGINE RUNNING

Fig. 489: Overdrive Range, First Gear Hydraulic Circuit Diagram Courtesy of GENERAL MOTORS CORP.

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