Chrysler Torqueflite Transmissions


Chrysler Torqueflite Transmissions

Chrysler Corporation introduced the Torqueflite transmission in 1956. This transmission was the first modern 3-speed automatic transmission with a torque converter and the first to use the Simpson 2-planetary compound gear train. Nearly all Torqueflite-based transmissions and transaxles use a rotor-type oil pump and all use a Simpson gear train.

There are two basic versions of the 3-speed Torqueflite transmission: the A-904 and the A-727. The 904 is the light-duty version, while the 727, is the heavy-duty version. The A-998 and A-999 transmissions are newer versions of the A-904. In 1978, the basic Torqueflite transmission was modified for use as a FWD transaxle. Torqueflite transaxles contain the same basic parts as the A-904 transmission, except a transfer shaft, final drive gears, and a differential unit have been added to the assembly.

All the Torqueflite-based transmissions and transaxles, used today, have two multiple disc clutches, an overrunning clutch, two servos and bands, and two planetary gearsets to provide three forward gear ratios and a reverse ratio. The two multiple-disc clutches are called the front and rear clutch packs. The servos and bands are also referred to by their location, front and rear, or by their function, kickdown and low/reverse.

Power flow through Torqueflite transmissions occurs by the engagement and disengagement of the clutches and bands. Refer to the clutch and band application chart below, while reading through the power flow.

Gear Selector Position

Operating Gear

Rear Clutch

Rear Band

Front Band

Front Clutch

One-way Clutch

P-Park

None

 

 

 

 

 

R-Reverse

Reverse

 

x

 

x

 

N-Neutral

None

 

 

 

 

 

D-Drive

1st gear

x

 

 

 

x

 

2nd gear

x

 

x

 

 

 

3rd gear

x

 

 

x

 

2-Man. 2nd

1st gear

x

 

 

 

x

 

2nd gear

x

 

x

 

 

1-Man. 1st

1st gear

x

 

 

 

 

Power Flow in Park/Neutral The power inputs the transmission through the turbine of the torque converter. When the gear selector is in park and neutral, the power flow ends at the front and rear clutches because neither are applied; therefore, no power is applied to the output shaft. When the selector is placed in park, a parking pawl is mechanically moved by the linkage and locks the parking gear to the transmission case. The parking gear is on the outer circumference of the governor support.

Power Flow In Reverse When the gear selector is placed into reverse, the front clutch is applied and engages the input shell and the sun gear. The rear band is also applied and holds the rear planetary carrier. The front clutch drives the sun gear in a clockwise direction. Because the rear planet carrier is held, the sun gear drives the rear planet gears in a counterclockwise direction. The rotation of the planet gears drives the rear ring gear and the output shaft in a counterclockwise direction, resulting in reverse gear with gear reduction.

Power Flow In First Gear When the gear selector is moved to the drive position, fully automatic shifting with three gear ranges is available. The shift points are determined by vehicle speed and load. When the transmission is operating in first gear, the rear clutch is applied and serves as the input member for the planetary gearset. Because the rear clutch is applied, input torque flows from the turbine of the torque converter through the input shaft to the rear clutch, which drives the front ring gear in a clockwise direction.

The front planetary carrier is splined to the output shaft and is, therefore, held by the weight of the vehicle and the drive wheels. This causes the ring gear to drive the front planet gears in a clockwise direction. The pinion gears, which are in mesh with the sun gear, rotate it counterclockwise. The rotation of the common sun gear causes the rear planet pinion gears to rotate in a clockwise direction. The planet gears cause the rear ring gear and the output shaft to turn in clockwise direction.

The rear planet carrier is held by the overrunning clutch whenever the engine's torque is driving the planetary unit. During coast or deceleration, the weight of the vehicle and its momentum drive the planetary units through the output shaft. This causes the rear carrier to rotate clockwise and release the one-way clutch. This results in a neutral condition and doesn't allow for engine braking.

When the gear selector is placed in manual low(1), the rear band and clutch are applied. The overrunning clutch holds the rear planet carrier, as does the rear band. The band holds the carrier during deceleration when the one-way clutch freewheels, this does allow foe engine braking during coasting.

Power Flow in Second Gear When the gear selector is in drive, the transmission will automatically shift from first to second gears when the vehicle speed has reached a particular point and some load is overcome. The rear clutch remains applied and the front band engages to hold the sun gear stationary. The input shaft causes the front ring gear to rotate clockwise. Because the sun gear is held, the planet gears walk around the sun gear and drive the front planetary carrier and output shaft in a clockwise, but speed-reduced, direction.

The rear planetary set is effective during this gear because the rear planet carrier is rotating clockwise. This allows the one-way clutch to freewheel, thereby providing a neutral condition in the rear planetary gearset.

Power Flow in Third Gear Third gear is a direct drive gear. When the transmission shifts into third, both the front and rear clutches become inputs for the planetary gearsets. This locks the gearsets into direct drive. Whenever two members of a gearset are locked together, the pinion gears are unable to rotate on their individual shafts and the planetary gearset is locked. In this transmission, the two members that locked together are the front ring gear and the sun gear.

Add-On Overdrive Chrysler's A-500 and A-518, which are four-speed automatic transmissions, are used exclusively in the mid-size Dodge Dakota and full-size Dodge RAM pick-ups and vans. Fourth gear is provided by a separate planetary gearset and controlled by an overdrive clutch, direct clutch, and overrunning clutch in the overdrive assembly attached to the rear of the transmission. In overdrive, the output ratio is 0.69 to 1.

Overdrive or fourth gear operation is controlled by a manually operated overdrive switch on the instrument panel. The electrical overdrive switch and the single board engine controller (SBEC) controls the overdrive solenoid on the valve body.

These transmissions have extra long extension housings that hold the additional planetary gearset. An additional shaft was also added to the basic three-speed models. This shaft serves as the output shaft. The three-speed output shaft became an intermediate shaft linking the output from the Simpson gear train to the overdrive assembly.

Power flow through the first three gears is the same as other Torqueflite transmissions. However, to control the operating of the overdrive planetary, two multiple-disc clutches (direct and overdrive clutches) and a one-way overrunning clutch is used. The intermediate shaft is locked to the output shaft whenever the one-way clutch is locked. This locking results in bypassing the overdrive planetary and provides for direct drive.

The direct clutch locks the sun and ring gears together to prevent freewheeling of the overrunning clutch during coasting and deceleration. This provides for engine braking. The spring used in the direct clutch assembly is a heavy tension single-coil spring that applies great holding force onto the clutch discs.

The intermediate shaft also drives the planetary carrier of the overdrive gearset. The the transmission shifts from third to fourth gear, the overdrive clutch piston moves the clutch's hub to relieve the spring tension on the direct clutch assembly. It also applies pressure to the overdrive clutch, which locks the sun gear to the transmission case. With the sun gear held, the planet carrier forces the ring gear and output shaft to rotate in an overdrive condition.

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