System Operation
Automatic Transmission - 6F50 and 6F55
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
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 8 km/h (5 mph). Transmission operation is the same below 8 km/h (5 mph) and in the LOW position.
1st Gear Above 8 km/h (5 mph) Clutch Application Chart
H = Holding
1st Gear LOW Position and Below 8 km/h (5 mph) Clutch Application Chart
H = Holding
1st Gear Above 8 km/h (5 mph) Solenoid Operation Chart
NC = Normally closed
NH = Normally high
NL = Normally low
1st Gear LOW Position and Below 8 km/h (5 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.
