When the range selector lever is moved to the Drive Range - D position from the Neutral - N position, the following hydraulic and electrical system changes occur to shift the transmission into Drive Range.

Manual Valve

In the Drive Range position, the manual valve routes clutch feed pressure into the drive fluid circuit.

Forward Clutch Applies

#1 Ball Check Valve: Located in the control valve body assembly, the #1 ball check valve remains unseated and routes drive fluid to the forward clutch.

Forward Clutch Assembly: Drive fluid is routed to the forward clutch piston to apply the forward clutch plates.

Pressure Regulation

Line Pressure Control Solenoid Valve: The line pressure control solenoid valve duty cycle is ramped up, increasing VBS signal - line control fluid pressure.

Line 2 Pressure Regulator Valve: Increased VBS signal fluid pressure, together with spring force, moves the line 2 pressure regulator valve against orificed line 2 fluid pressure to increase the amount of tier 2 feed fluid pressure that is regulated into the line 2 circuit.

Line Limit Valve: Increased line 2 fluid pressure is routed to the line limit valve where it is regulated against spring force into the line 2 limit fluid circuit, increasing line 2 limit fluid pressure.

Clutch Boost Valve: Increased line 2 limit fluid is routed to the clutch boost valve and moves the valve against spring force and enters the clutch boost fluid circuit.

Forward and Reverse Clutch Valve: Clutch boost fluid is routed to the forward and reverse clutch valve where it assists spring force and moves the valve against VBS signal and orificed clutch control fluid pressures. This allows increased line 2 limit fluid pressure to increase the amount of fluid pressure in the clutch control circuit.

TCC Control Valve: Increased clutch control fluid pressure passes through the TCC control valve and increases the pressure in the clutch feed circuit. This allows extra fluid pressure to enter the drive circuit, at the manual valve, in order to provide additional force to apply the forward clutch plates.

Ratio Control

Important: Remember that the function of an orifice is to control the flow rate of fluid and the rate of apply or release of a clutch or pulley

Ratio Control Motor and Variable Ratio Control Valve: The ratio control motor is activated by the TCM, in response to throttle position, and moves the variable ratio control valve against spring force. This allows line 1 fluid to be regulated into the primary feed circuit.

Primary Limit Valve: Primary feed fluid is routed to the primary limit valve where it is regulated against spring force into the primary feed limit circuit.

#3 Ball Check Valve: Located in the control valve body assembly, primary feed fluid seats the #3 ball check valve and passes through orifice #24 into the primary feed limit circuit. This orifice helps to control variable drive pulley assembly apply.

Variable Drive Pulley Assembly Applied: Primary feed limit fluid enters the variable drive pulley assembly and acts on the variable drive pulley piston to control the variable drive ratio.

Intermediate and Low Ranges

Intermediate Range may be selected at any time while the vehicle is being operated in a forward range. However, TCM control prevents the transmission from operating in a high ratio. When the range selector lever is moved to Intermediate Range - INT from Drive Range - D, the manual valve also moves. There are no changes to the hydraulic system but, the Park/Neutral position switch assembly signals the TCM that the transmission is in Intermediate Range.

Low Range may also be selected at any time while the vehicle is being operated in a forward range. However, TCM control limits the transmission to lower ratios only. When the range selector lever is moved to Low Range - LO from Drive Range - D or Intermediate Range - INT, the manual valve also moves. There are no changes to the hydraulic system but, the Park/Neutral position switch assembly signals the TCM that the transmission is in Low Range.

Important: Power flow for Drive, Intermediate and Low is exactly the same except the ratio is changed - controlled differently in each range. Drive range allows the full range of ratios from high to low. Intermediate does not allow the high ratios, and low is limited to only the lower ratios.

Drive, Intermediate and Low Range - TCC Released