Component Description

Hydraulic System - 6F50 and 6F55

Component Description

Transmission Pump and Fluid Filter

The transmission fluid in the sump area at the bottom of the transmission case flows through a transmission fluid filter to the pump assembly. The pump is bolted to the torque converter housing and is chain driven from a sprocket that is mounted on the stator support and turned by the torque converter.










Transmission Fluid Level

The transmission fluid level is checked with the transmission at normal operating temperature between 82.3 C (180 F) and 93.4 C (200 F).

The transmission fluid level indicator is part of the filler cap.

The correct transmission fluid level is between the MIN and MAX in the cross hatches of the transmission fluid level indicator.










Main Control

The hydraulic system has a main control assembly. The main control assembly consists of a valve body and a solenoid body. The valve body contains the hydraulic regulator and multiplex shift valves. The solenoid body contains the shift solenoids that control the hydraulic valves. The solenoid body is serviced as an assembly and can not be disassembled. The solenoid body is controlled by the PCM (Powertrain Control Module). The PCM (Powertrain Control Module) has software stored in it specific to the solenoid body currently in the transmission, called the solenoid body strategy. A new solenoid body strategy must be downloaded into the PCM (Powertrain Control Module) any time a new solenoid body is installed.







































Multi-Plate Clutch

Multi-plate clutches are clutches that consist of multiple friction and steel clutch discs that when pressure is applied, either drive or hold (brake) components of the planetary gearset. This transmission has 5 multi-plate clutches:
- Forward (1,2,3,4)
- Direct (3,5,R)
- Intermediate (2,6)
- Overdrive (4,5,6)
- Low/reverse
Both the direct (3,5,R) and the overdrive (4,5,6) clutches are drive clutches. The direct (3,5,R) clutch drives the rear planetary sun gear and the overdrive (4,5,6) clutch drives the rear planetary carrier. The forward (1,2,3.4), intermediate (2,6) and the low/reverse clutches are brake clutches. The forward (1,2,3,4) clutch holds the front sun gear, the intermediate (2,6) clutch holds the rear sun gear and the low/reverse clutch holds the rear planetary carrier.

Clutches; overdrive (4,5,6) and direct (3,5,R) are balanced in terms of dynamic pressure. That is, their pistons are exposed to the transmission fluid flow on both sides to prevent pressure buildup in the clutch as speed increases. This dynamic pressure equalization process is achieved by a baffle plate and pressure-free transmission fluid supply by a lubricating passage, through which the space between the piston and baffle plate is filled with transmission fluid.

The advantages of this dynamic pressure equalization are:
- reliable clutch engagement and release in all speed ranges.
- improved shift refinement.

External sealing

The torque converter housing has a lip-type seal that seals the torque converter hub. The manual control lever shaft and half shafts also use lip-type seals. AWD (All-Wheel Drive) vehicles do not use a RH (Right Hand) half shaft seal, the transmission is sealed by the PTU (Power Transfer Unit) on the RH (Right Hand) side.

The torque converter housing is sealed to the transmission case with silicone sealant.

The transmission cover is sealed to the transmission case with a reusable gasket. The main control cover is sealed to the transmission case and the solenoid body with reusable rubber gaskets.

The TSS (Turbine Shaft Speed) sensor is sealed to the transmission cover with an O-ring seal. The transmission fluid filler tube is sealed to the main control cover with an O-ring seal that is serviced with the transmission fluid filler tube. The transmission fluid level indicator is sealed to the transmission fluid filler tube with an O-ring seal that is serviced with the transmission fluid level indicator.

The line pressure tap plug, transmission fluid drain plug and the lubrication circuit tap plug have pipe threads and seal when tightened to specification.










Hydraulic Circuits Legend





Line Pressure Hydraulic Circuits

The PCM (Powertrain Control Module) controls line pressure with the LPC (Line Pressure Control) solenoid. This affects shift feel and apply component operation.

When the engine is running, the pump supplies pressure to the pressure regulator valve, which is controlled by the LPC (Line Pressure Control) solenoid. The pressure regulator valve controls the line pressure.

The line pressure circuit supplies the manual valve. The manual valve directs the line pressure to either the REV/REV SUPPLY circuit when the manual control lever is in the REVERSE position or the DRIVE 1 circuit when the manual control lever is in the DRIVE or LOW position.





Lubrication Hydraulic Circuits

Lubrication for the transmission is supplied by the transmission fluid cooler return tube. Transmission fluid is sent to the transmission fluid cooler from the torque converter clutch control valve.

LINE pressure supplied to the pressure regulator valve is sent to the torque converter clutch control valve as CONV FD pressure. During TCC (Torque Converter Clutch) release, the torque converter clutch control valve sends the transmission fluid to the torque converter to release the clutch. The transmission fluid returns to the torque converter clutch control valve from the torque converter and is directed to the transmission fluid cooler on the COOLER FEED circuit.









Torque Converter Hydraulic Circuits

The PCM (Powertrain Control Module) controls the TCC (Torque Converter Clutch) solenoid. The TCC (Torque Converter Clutch) solenoid applies hydraulic pressure to the torque converter clutch control and regulator apply valves through the TCC SOL SIG circuit. Regulated DRIVE 2 pressure from the multiplex shift valve is directed to the torque converter clutch control valve by the torque converter clutch regulator apply valve through the REG APPLY circuit. The torque converter clutch control valve directs pressure from the REG APPLY circuit to the TCC APPLY circuit to apply the clutch.

The transmission fluid returns to the torque converter clutch control valve through the TCC RELEASE hydraulic circuit. The torque converter clutch control valve opens the TCC RELEASE circuit to exhaust, so the TCC RELEASE circuit is not pressurized when the TCC (Torque Converter Clutch) is applied.





When the TCC (Torque Converter Clutch) is released, The TCC (Torque Converter Clutch) solenoid does not apply hydraulic pressure to the torque converter clutch control or regulator apply valves. The torque converter clutch control valve, in this position, directs hydraulic pressure from the CONV FD circuit to the torque converter through the TCC RELEASE hydraulic circuit and it returns to the torque converter clutch control valve through the TCC APPLY circuit.





Solenoid Hydraulic Circuits

LINE pressure from the pump is directed to the individual shift, TCC (Torque Converter Clutch) and LPC (Line Pressure Control) solenoids by the solenoid regulator valve on the SOL FEED circuit. The solenoids, controlled by the PCM, direct the fluid to the valves that they control.

The LPC (Line Pressure Control) solenoid sends varying pressure to the line pressure regulator valve to control line pressure.





Forward Clutch Hydraulic Circuits

When the forward (1, 2, 3, 4) clutch is applied in 1st (above 8 km/h (5 mph), 2nd, 3rd and 4th gears, LINE pressure from the pump is directed to the multiplex shift valve by the manual valve through the DRIVE 1 hydraulic circuit. The multiplex shift valve supplies the forward (1, 2, 3, 4) clutch regulator valve with pressure through the DRIVE 2, CB26FD/CB1234FD and CB1234 SUP hydraulic circuits. The forward (1, 2, 3, 4) clutch regulator valve directs regulated pressure to the forward (1, 2, 3, 4) clutch through the CB1234 hydraulic circuit





When the forward (1, 2, 3, 4) clutch is applied in LOW position and 1st gear (below 8 km/h (5 mph)), LINE pressure from the pump is directed to the multiplex shift valve by the manual valve through the DRIVE 1 hydraulic circuit. The multiplex shift valve directs the pressure to the multiplex manual valve through the REV DRIVE B circuit. The multiplex manual valve directs the REV DRIVE B pressure to the forward (1, 2, 3, 4) clutch regulator valve through the DRIVE B, CB26FD/CB1234FD and CB1234 SUP circuits. SSA (Shift Solenoid A) supplies varying solenoid pressure to the CB1234 clutch regulator and boost valves. As the CB1234 clutch regulator valve moves, it supplies the forward (1, 2, 3, 4) clutch and CB1234 boost valve with regulated line pressure through the CB1234 circuit. The CB1234 boost valve directs the regulated line pressure to the opposite side of the regulator valve through the CB1234 FDBK circuit for controlled forward (1, 2, 3, 4) clutch engagement.





Direct (3, 5, R) Clutch Hydraulic Circuits

When the direct (3, 5, R) clutch is applied in REVERSE, LINE pressure from the pump is directed to the multiplex manual valve by the manual valve through the REV hydraulic circuit. The multiplex manual valve supplies the direct (3, 5, R) clutch regulator valve with pressure through the REV SUPPLY and C35R SUPPLY hydraulic circuits. To apply the direct (3, 5, R) clutch, SSB (Shift Solenoid B) applies varying solenoid pressure to the C35R clutch regulator and boost valves. As the C35R regulator valve moves, it supplies the direct (3, 5, R) clutch and C35R boost valve with regulated line pressure through the C35R circuit. The C35R boost valve directs the regulated line pressure to the opposite side of the C35R clutch regulator valve through the C35R FDBK circuit for controlled direct (3, 5, R) clutch engagement.





When the direct (3, 5, R) clutch is applied in 3rd and 5th gears, LINE pressure from the pump is directed to the multiplex shift valve by the manual valve through the DRIVE 1 hydraulic circuit. The multiplex shift valve directs the pressure to the direct (3, 5, R) clutch regulator valve through the DRIVE 2/C35R SUPPLY circuits. To apply the direct (3, 5, R) clutch, SSB (Shift Solenoid B) applies varying solenoid pressure to the C35R clutch regulator and boost valves. As the C35R regulator valve moves, it supplies the direct (3, 5, R) clutch and C35R boost valve with regulated line pressure through the C35R circuit. The C35R boost valve directs the regulated line pressure to the opposite side of the C35R clutch regulator valve through the C35R FDBK circuit for gradual direct (3, 5, R) clutch engagement.





Intermediate (2, 6) Clutch Hydraulic Circuits

When the intermediate (2, 6) clutch is applied in 2nd and 6th gears, LINE pressure from the pump is directed to the multiplex shift valve by the manual valve through the DRIVE 1 hydraulic circuit. The multiplex shift valve supplies the intermediate (2, 6) clutch regulator valve with pressure through the DRIVE 2 and CB26FD/CB1234FD hydraulic circuits. The intermediate (2, 6) clutch regulator valve is controlled by SSC (Shift Solenoid C) and directs regulated pressure to the intermediate (2, 6) clutch through the CB26 hydraulic circuit. The CB26 hydraulic circuit also supplies pressure to the opposite side of the CB26 clutch regulator valve for controlled intermediate (2, 6) clutch engagement. Regulated overdrive (4, 5, 6) clutch pressure is supplied to the intermediate (2, 6) clutch regulator valve in 6th gear to boost the SSC (Shift Solenoid C) solenoid pressure.





Low - Reverse Clutch Hydraulic Circuits

When the low/reverse clutch is applied in REVERSE, LINE pressure from the pump is directed to the multiplex shift valve by the manual valve through the REV hydraulic circuit to move the valve. Line pressure is also supplied to the low/reverse/overdrive clutch regulator valve from the pump. The low/reverse/overdrive clutch regulator valve is controlled by SSD (Shift Solenoid D) and directs regulated pressure to the multiplex shift valve. The multiplex shift valve directs the regulated pressure to the low/ reverse clutch through the CBLR SUPPLY circuit.





When the low/reverse clutch is applied in PARK, LOW or 1st gear below 8 km/h (5 mph), SSE (Shift Solenoid E) pressure is supplied to the multiplex shift valve to move the valve. LINE pressure is supplied to the low/ reverse/overdrive clutch regulator valve from the pump. The low/reverse/overdrive clutch regulator valve is controlled by SSD (Shift Solenoid D) and directs regulated pressure to the multiplex shift valve. The multiplex shift valve directs the regulated pressure to the low/reverse clutch through the CBLR SUPPLY circuit.





Overdrive Clutch Hydraulic Circuits

When the overdrive clutch is applied in 4th, 5th and 6th gears, LINE pressure is supplied to the low/reverse/ overdrive (4, 5, 6) clutch regulator valve from the pump. To apply the overdrive (4, 5, 6) clutch, SSD (Shift Solenoid D) applies varying solenoid pressure to the CBLR/C456 regulator and boost valves. As the CBLR/C456 regulator valve moves, it supplies the multiplex shift valve assembly and CBLR/C456 boost valve with regulated line pressure through the CBLR/C456 SUPPLY circuit. The CBLR/C456 boost valve directs the regulated line pressure to the opposite side of the CBLR/C456 regulator valve through the CBLR/C456 FDBK circuit for controlled overdrive (4, 5, 6) clutch engagement. The multiplex shift valve directs the regulated pressure to the multiplex manual valve through the C456 SUPPLY hydraulic circuit. The multiplex manual valve directs the regulated pressure to the overdrive (4, 5, 6) clutch through the C456 hydraulic circuit. The C456 circuit also supplies pressure to the CB26 clutch regulator valve to boost the pressure from SSC (Shift Solenoid C) in 6th gear.