Automatic Transmission - 6F50 and 6F55
Automatic Transmission - 6F50 and 6F55
Component Location
Overview
This automatic transmission is a 6-speed transmission with electronic shift control. It is designed for operation in a transverse powertrain for FWD (Front Wheel Drive) and AWD (All-Wheel Drive) vehicles.
This transmission has the following features:
- Six forward speeds
- Torque converter with an integral converter clutch
- Electronic shift and pressure controls
- Three planetary gearsets
- Three fixed multi-disc clutches
- Two multi-plate drive clutches
All hydraulic functions are directed by electronic solenoids to control the following:
- Engagement feel
- Shift feel
- Shift scheduling
- Modulated TCC (Torque Converter Clutch) applications
This transmission has a main control which contains:
- Solenoid body with TFT (Transmission Fluid Temperature) sensor
- Upper Valve body
- Lower Valve body
This automatic transmission is an electronically controlled transmission. Gear selection is achieved by the control of transmission fluid flow to operate various internal clutches. The PCM (Powertrain Control Module) operates the electrical components and provides control of gear selection shift pressure, which increases refinement and torque converter slip.
In the event of a system fault, the PCM (Powertrain Control Module) also provides for Failure Mode Effect Management to maintain maximum functional operation of the transmission with a minimum power reduction. In the event of a total loss of control or electrical power, the basic transmission functions P, R, N and D are retained. Also 5th gear is retained by the hydraulic system.
Identification Tags
Identification Tag Location
Transmission Identification Tag
Original Solenoid Body Tag
Replacement Solenoid Body Tag
Solenoid Body Identification Tag
System Operation
Park
Park Clutch Application Chart
H = Holding
Park Position Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
Powerflow
- With the selector lever in PARK, the low/reverse clutch holds the rear planetary carrier/center ring gear stationary.
- The parking pawl holds the rear ring/front planetary carrier stationary
- The turbine shaft drives the center sun gear
Reverse
Reverse Clutch Application Chart
H = Holding
D = Driving
Reverse Position Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
Power Flow
- With the selector lever in REVERSE, the low/reverse clutch holds the rear planetary carrier/center ring gear stationary.
- The direct clutch drives the rear sun gear.
- The rear ring/front planetary carrier transfers torque to the output hub in a reverse direction with a ratio of 2.88.
Neutral
Neutral Position Clutch Application Chart
H = Holding
Neutral Position Solenoid Operation Chart
a Solenoid state will change if vehicle is moving forward with the selector lever in the NEUTRAL position.
NC = Normally closed
NH = Normally high
NL = Normally low
Power Flow
- With the selector lever in NEUTRAL, the low/reverse clutch holds the rear planetary carrier/center ring gear stationary.
- The turbine shaft drives the center sun gear
1st Gear
NOTE: The transmission operates differently in 1st gear above and below 4.8 kmh (3 mph). Transmission operation is the same below 4.8 kmh (3 mph) and in the LOW position.
1st Gear Above 4.8 kmh (3 mph) Clutch Application Chart
H = Holding
1st Gear LOW Position and Below 4.8 kmh (3 mph) Clutch Application Chart
H = Holding
1st Gear Above 4.8 kmh (3 mph) Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
1st Gear LOW Position and Below 4.8 kmh (3 mph) Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
Power Flow
- In first gear, the forward clutch holds the front sun gear stationary.
- The rear planetary carrier/center ring gear is held stationary by the low OWC (One-Way Clutch) and / or the low reverse (1,R) clutch.
- The turbine shaft transfers torque to the center sun gear. The center sun gear transfers the torque to the center planetary carrier/front ring gear. The front ring gear transfers torque to the front planetary carrier/rear ring gear and the output hub to produce a ratio of 4.48.
2nd Gear
2nd Gear Clutch Application Chart
H = Holding
2nd Gear Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normal low
Power Flow
- In second gear the forward clutch holds the front sun gear stationary.
- The intermediate clutch holds the rear sun gear stationary.
- The turbine shaft transfers torque to the center sun gear. The center sun gear transfers torque to the center ring gear/rear planetary carrier.
- The rear planetary carrier transfers the torque to the rear ring gear/front planetary carrier and the output hub to produce a gear ratio of 2.87.
3rd Gear
3rd Gear Clutch Application Chart
H = Holding
D = Driving
3rd Gear Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
Power Flow
- In third gear the forward clutch holds the front sun gear stationary.
- The direct clutch drives the rear sun gear.
- Power flows from the center sun gear to the center planetary carrier/front ring gear. From there, torque is transferred to the rear ring gear/front planetary carrier.
- Power also flows from the rear sun gear to the rear ring gear/front planetary carrier.
- The two inputs to the front planetary carrier combine and transfer torque to the output hub to produce a gear ratio of 1.84.
4th Gear
4th Gear Clutch Application Chart
H = Holding
D = Driving
4th Gear Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
Power Flow
- In fourth gear the forward clutch holds the front sun gear stationary.
- The overdrive clutch drives the rear planetary carrier/center ring gear.
- Power flows from turbine shaft to the center sun gear and center ring gear.
- The two inputs to the center planetary carrier combine and transfer torque to the front ring gear.
- The front ring gear transfers the torque to the front planetary carrier and onto the output hub to produce a gear ratio of 1.41.
5th Gear
5th Gear Clutch Application Chart
D = Driving
5th Gear Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
Power Flow
- In fifth gear the overdrive clutch drives the rear planetary carrier/center ring gear.
- The direct clutch drives the rear sun gear.
- The turbine shaft transfers torque to the center sun gear, rear sun gear, and rear planetary carrier/center ring gear.
- The torque from the three inputs locks the three planetary gearsets which produces a gear ratio of 1 to 1
Failsafe Mode
Because both SSD (Shift Solenoid D) and SSB (Shift Solenoid B) apply the clutches they control when they are turned OFF, 5th gear is the fail-safe.
6th Gear
6th Gear Clutch Application Chart
H= Holding
D = Driving
6th Gear Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
Power Flow
- In sixth gear the overdrive clutch drives the rear planetary carrier/center ring gear.
- The intermediate clutch holds the rear sun gear.
- The torque from the rear planetary carrier is transferred to the rear ring gear/front planetary carrier and the output hub which produces a gear ratio of 0.74.
