AW-4 4-Speed
ELECTRONIC CONTROLSThe AW-4 is electronically controlled in 1, 2, 3 and D ranges. Controls consist of the Transmission Control Module (TCM), valve body solenoids and various sensors. The sensors monitor vehicle speed, throttle opening, shift lever position and brake pedal application.
TRANSMISSION CONTROL MODULE (TCM)
The module determines shift and converter clutch engagement timing based on signals from sensors. The valve body solenoids are activated, or deactivated accordingly.
The TCM has a self diagnostic program. Component and circuitry malfunctions can be diagnosed with the DRB scan tool. Once a malfunction is noted and stored in control module memory, it is retained even after the problem has been corrected. To cancel a stored malfunction, disconnect and reconnect the "Trans." fuse in the module harness.
TRANSMISSION VALVE BODY SOLENOIDS
The solenoids are mounted on the valve body and operated by the TCM. The solenoids control operation of the converter clutch and shift valves in response to input signals from the module.
SENSORS
Sensors include:
- Throttle Position Sensor (TPS)
- transmission speed sensor
- vehicle speed sensor
- park/neutral position switch
- brake switch
The throttle position sensor is mounted on the throttle body. It electronically determines throttle position and relays this information to the transmission control module to determine shift points and converter clutch engagement.
The transmission speed sensor consists of a rotor and magnet on the transmission output shaft and a switch in the extension housing or adapter. The sensor switch is activated each time the rotor and magnet complete one revolution. Sensor signals are sent to the transmission control module.
The park/neutral position switch is mounted on the valve body manual shaft. The switch signals shift linkage and manual valve position to the transmission control module through an interconnecting harness. The switch prevents engine starting in all gears other than Park or Neutral.
The brake switch is in circuit with the torque converter clutch solenoid. The switch disengages the converter clutch whenever the brakes are applied. The switch is mounted on the brake pedal bracket and signals the transmission control module when the pedal is pressed or released.
TORQUE CONVERTER
A three element torque converter is used for all applications. The converter contains an impeller, stator, and turbine.
Torque Converter (With Clutch):
The AW-4 converters are all equipped with a converter clutch mechanism. The clutch consists of a sliding clutch piston, clutch springs and the clutch disc material. The clutch provides optimum torque transfer and economy when engaged.
The clutch disc is attached to the converter front cover. The clutch piston and clutch springs are attached to the turbine hub. The springs dampen engine firing impulses and loads during the initial phase of converter clutch engagement.
Clutch engagement is controlled by transmission valve body solenoid number three and by the converter clutch relay valve. The solenoid channels line pressure to the clutch through the relay valve at clutch engagement speeds.
Torque converter clutch engagement occurs in second gear in 1-2 position; third gear in 3 position and third and fourth gear in D position.
FOURTH GEAR OVERDRIVE COMPONENTS
Forth Gear Overdrive Components:
The overdrive system consists of the input shaft, one-way clutch, planetary sun gear, ring gear, planetary carrier, overdrive clutch and overdrive brake. The overdrive elements are controlled and applied through transmission valve body solenoid number two.
In fourth gear, the overdrive brake prevents the overdrive sun gear from turning. The overdrive input shaft and planetary carrier rotate as a unit. The sun gear and overdrive direct clutch drum are in mesh and operate as a single unit. The direct clutch splines function as the hub for the overdrive brake. The one-way clutch outer race is in mesh with the planetary carrier. The inner race is fixed to the sun gear shaft.
FIRST/SECOND/THIRD/REVERSE GEAR COMPONENTS
First/Second/Third/Reverse Gear Components:
First through third and reverse gear components are outlined in.
The input shaft is meshed with the direct clutch hub and the forward clutch drum. These elements rotate as a unit. The forward clutch hub rotates as a unit with the front planetary ring gear. The direct clutch drum is meshed with the forward end of the planetary sun gear.
The second brake hub serves as the outer race of one-way clutch No. 1. The clutch inner race is locked with the front/rear sun gear. The inner race of one-way clutch No. 2 is splined to the transmission case and is locked. The outer race rotates as a unit with the rear planetary carrier.
The rear planetary ring gear is splined to the output shaft. The front planetary carrier and rear carrier ring gear are meshed and rotate as a unit with the output shaft.
GEARTRAIN OPERATION AND APPLICATION CHARTS
Operation and application of the first through fourth and reverse gear elements are outlined in the function and application charts.
The Component Function Chart describes basic function of various geartrain elements. The Component Application Chart indicates which elements (including valve body solenoids), are applied in the various gear ranges.
HYDRAULIC SYSTEM
The hydraulic system consists of the pump, valve body and solenoids, and four hydraulic accumulators. The oil pump provides lubrication and operating pressure.
The valve body controls application of the clutches, brakes, second coast band, and the converter clutch. The valve body solenoids control sequencing of the 1-2, 2-3 and 3-4 shift valves. The solenoids are activated by signals from the transmission control module.
The accumulators are used in the clutch and brake feed circuits to control initial apply pressure. Spring loaded accumulator pistons modulate the initial surge of apply pressure for smooth engagement.
OIL PUMP
A gear-type oil pump is used. The pump gears are mounted in the pump body. The pump drive gear is operated by the torque converter hub. Drive tangs on the hub engage in drive slots in the drive gear.
TRANSMISSION VALVE BODY COMPONENTS
Upper Body Components:
Transmission operating pressure is supplied to the clutch and brake apply circuits through the transmission valve body. The valve body consists of an upper body, lower body, separator plate and upper and lower gaskets. The various spool valves, sleeves, plugs and springs are located within the two body sections.
Two-Section Transmission Valve Body:
Lower Body Components:
The manual valve, 1-2 shift valve, primary regulator valve, accumulator control valve, check balls, solenoids and oil strainers are located in the lower body section. The remaining control and shift valves plus check balls and one additional oil strainer are located in the upper body section.
MANUAL VALVE
Manual Valve:
The manual valve is operated by the gearshift linkage. The valve diverts fluid to the apply circuits according to shift lever position.
PRIMARY REGULATOR VALVE
Primary Regulator Valve:
The primary regulator valve modulates line pressure to the clutches and brakes according to engine load. The valve is actuated by throttle valve pressure.
During high load operation, the valve increases line pressure to maintain positive clutch and brake engagement. At light load, the valve decreases line pressure just enough to maintain smooth engagement.
THROTTLE VALVE AND DOWNSHIFT PLUG
Throttle Valve And Downshift Plug:
The throttle valve and downshift plug control throttle pressure to the primary regulator valve.
The downshift plug and throttle valve are operated by the throttle valve cam and throttle cable in response to engine throttle position. Throttle valve pressure is also modulated by the cut-back valve in second, third and fourth gear ranges.
CUT-BACK VALVE
Cut-Back Valve:
The cut-back valve helps prevent excessive pump pressure buildup in second, third and fourth gear. The valve is actuated by throttle pressure and by line pressure from the second brake. The valve also helps regulate line pressure by controlling the amount of cut-back pressure to the throttle valve.
SECONDARY REGULATOR VALVE
Secondary Regulator Valve:
The secondary regulator valve regulates converter clutch and transmission lubrication pressure. When primary regulator valve pressure exceeds requirements for clutch engagement or transmission lubrication, the secondary regulator valve is moved upward exposing the drain port. Excess pressure then bleeds off as needed. As pressure drops, spring tension moves the valve downward closing the drain port.
CONVERTER CLUTCH RELAY VALVE
Converter Clutch Relay Valve:
The converter clutch relay valve controls fluid flow to the converter clutch. The valve is operated by line pressure from the 1-2 shift valve and is controlled by solenoid valve number three.
1-2 SHIFT VALVE
1 - 2 Shift Valve:
The 1-2 shift valve controls the 1-2 upshifts and downshifts. The valve is operated by the No. 2 valve body solenoid and line pressure from the manual valve, second coast modulator valve and the 2-3 shift valve.
When the transmission control module deactivates the solenoid, line pressure at the top of the valve moves the valve down closing the second brake accumulator feed port. As the solenoid is activated and the drain port opens, spring force moves the valve up exposing the second brake feed port for the shift to second gear.
2-3 SHIFT VALVE
2 - 3 Shift Valve:
The 2-3 shift valve controls the 2-3 upshifts and downshifts. The valve is actuated by the No. 1 valve body solenoid and by line pressure from the manual valve and primary regulator valve.
When the TCM activates solenoid No. 1, line pressure at the top of the 2-3 valve is released through the solenoid drain port. Spring tension moves the valve up to hold the valve in second gear position. As the solenoid is deactivated, line pressure then Moves the valve down exposing the direct clutch feed port for the shift to third gear.
3-4 SHIFT VALVE
3 - 4 Shift Valve:
The 3-4 shift valve is operated by the No. 2 solenoid and by line pressure from the manual valve, 2-3 valve and primary regulator valve.
Energizing the No. 2 solenoid causes line pressure at the top of the 3-4 valve to be released through the solenoid valve drain port. Spring tension moves the valve up exposing the overdrive clutch accumulator feed port to apply the clutch.
De-energizing the solenoid causes the drain port to close. Line pressure then moves the valve down exposing the overdrive brake accumulator feed port for the shift to fourth gear.
In the 1-2 or 3 gearshift lever positions, line pressure from the 2-3 shift valve is applied to the lower end of the 3-4 valve. This holds the valve upward, closing off the overdrive brake feed port preventing a shift into fourth gear.
SECOND COAST MODULATOR VALVE
Second Coast Modulator Valve:
The second coast modulator valve momentarily reduces line pressure from the 1-2 shift valve. This cushions application of the second coast brake. The valve is operative when the shift lever and manual valve are in the 3 position.
LOW COAST MODULATOR VALVE
Low Coast Modulator Valve:
The low coast modulator valve momentarily reduces line pressure from the 2-3 shift valve; this action cushions application of the first/reverse brake. The modulator valve operates when the shift lever and manual valve are in the 1-2 position.
ACCUMULATOR CONTROL VALVE
Accumulator Control Valve:
The accumulator control valve cushions the transmission clutch and brake applications. This is achieved by reducing back pressure to the accumulators when throttle opening is small. The valve is operated by line and throttle pressure.
ACCUMULATORS
Accumulators:
Four accumulators are used to cushion clutch and brake application. The accumulators, consist of spring loaded pistons. The pistons dampen the initial surge of apply pressure to provide smooth engagement during shifts.
Control pressure from the accumulator control valve is continuously applied to the back pressure side of the accumulator pistons. This pressure plus spring tension holds the pistons down. As line pressure from the shift valves enters the opposite end of the piston bore, control pressure and spring tension momentarily delay application of full line pressure to cushion engagement. The accumulators are all located in the transmission case.
TRANSMISSION VALVE BODY SOLENOIDS
Transmission Valve Body Solenoids:
Three solenoids are used. The No. 1 and 2 solenoids control shift valve operation by applying or releasing line pressure. The signal to apply or release pressure is provided by the transmission control module.
The No. 3 solenoid controls operation of the torque converter clutch. The solenoid operates in response to signals from the transmission control module.
When the No. 1 and 2 solenoids are activated, the solenoid plunger is moved off its seat opening the drain port to release line pressure. When either solenoid is deactivated, the plunger closes the drain port.
The No. 3 solenoid operates in reverse. When the solenoid is deactivated, the solenoid plunger is moved off its seat opening the drain port to release line pressure. When the solenoid is activated, the plunger closes the drain port.
TRANSMISSION COOLER
MAIN COOLER
The transmission main cooler is located in the radiator. The main cooler can be flushed when necessary, however, the cooler is not a repairable component. If the cooler is damaged, plugged, or leaking, the radiator will have to be replaced.
AUXILIARY COOLER
Auxiliary Cooler Mounting (Left Hand Drive):
The auxiliary cooler is mounted in front of the radiator at the driver side of the vehicle. The cooler can be flushed when necessary, while mounted in the vehicle. The cooler can also be removed for access, repair, or replacement as needed.
The main and auxiliary coolers should both be flushed whenever a transmission or converter clutch malfunction generates sludge, debris, or particles of clutch friction material.
COOLER SERVICE
The main cooler (and radiator) and the auxiliary cooler can be removed for service or access to other components. Auxiliary cooler removal requires that the front bumper and radiator support be removed for access to the cooler lines and attaching bracket.
BRAKE TRANSMISSION SHIFT INTERLOCK MECHANISM
Ignition Interlock Cable Routing:
Ignition Key Cylinder Actuation:
The Brake Transmission Shifter/Ignition Interlock (BTSI), is a cable and solenoid operated system. It interconnects the automatic transmission floor mounted shifter to the steering column ignition switch. The system locks the shifter into the PARK position. The Interlock system is engaged whenever the ignition switch is in the LOCK or ACCESSORY position. An additional electrically activated feature will prevent shifting out of the PARK position unless the brake pedal is depressed at least one-half an inch. A magnetic holding device in line with the park/brake interlock cable is energized when the ignition is in the RUN Position. When the key is in the RUN position and the brake pedal is depressed, the shifter is unlocked and will move into any position. The interlock system also prevents the ignition switch from being turned to the LOCK or ACCESSORY position unless the shifter is fully locked into the PARK position.