Powertrain

POWERTRAIN DESCRIPTION





COMPONENT DESCRIPTIONS





NOTE:
- All directions of rotation are viewed from the oil pump.

2/4 BAND





The LA4A-EL transaxle has a 2/4 band that allows the case to hold the reverse clutch drum and Reverse/fourth gear (REV/4GR) sun gear stationary in 2GR and 4GR.
The 2/4 band has one end anchored in the transaxle case.
The reverse clutch drum is connected to the shell of the REV/4GR sun gear, with the mating lug teeth.

2/4 BAND APPLY
- Fluid in the Servo Apply (SA) circuit pushes the servo piston and its apply rod (selective length) against returning spring force.
- The apply rod pushes one end of the band, causing the band to squeeze around the reverse clutch drum.
- The 2/4 band and the reverse clutch drum are connected, due to friction.

REVERSE CLUTCH





The LA4A-EL transaxle has a reverse clutch that connects these components in R position:
- The reverse clutch hub
- The reverse clutch drum

The turbine shaft with spline teeth is connected to F/C/D: Forward/Coasting/Direct clutch cylinder and also with spline teeth, which are connected to the reverse clutch hub. When the reverse clutch is applied, the reverse clutch hub is connected to the reverse clutch drum. The reverse clutch drum is then connected to the shell of the REV/4GR sun gear, with the mating lug teeth.

REVERSE CLUTCH APPLY
- Fluid in the Reverse Clutch (RC) circuit pushes the clutch piston against returning spring force.
- The piston pushes the clutch plates against a retaining ring on selective thickness.
- The reverse clutch hub and housing are connected, due to friction.

DIRECT CLUTCH





The LA4A-EL transaxle has a direct clutch that connects these components in 3GR and 4GR:
- The F/C/D: Forward/Coasting/Direct clutch cylinder
- The direct clutch shell

The turbine shaft is connected to the F/C/D clutch cylinder with spline teeth. When the direct clutch is applied, the F/C/D clutch cylinder is connected to the direct clutch shell. The direct clutch shell connects to the LOW-INT Low-Intermediate ring gear by using mating lug teeth. The ring gear is splined to the REV/4GR carrier.

DIRECT CLUTCH APPLY
- Fluid in the Direct Clutch (DC) circuit pushes the clutch piston against spring force.
- The piston pushes the clutch plates against a retaining ring on selective thickness.
- The F/C/D clutch housing and direct clutch shell are connected, due to friction.

FORWARD CLUTCH





The LA4A-EL transaxle has a forward clutch that connects these components in all forward gears although it does not transmit torque in 4GR because the forward one-way clutch is overrunning:
- The F/C/D: Forward/Coasting/Direct clutch cylinder
- The outer race of forward one-way clutch

When the forward clutch is applied, the F/C/D clutch cylinder is connected to the forward one-way outer race. The turbine shaft is connected to the F/C/D clutch cylinder with spline teeth. The outer race of the forward one-way clutch connects to the LOW-INT. low-intermediate sun gear.

FORWARD CLUTCH APPLY
- Fluid in the Forward Clutch (FC) circuit pushes the clutch piston against spring force.
- The clutch piston pushes the clutch plates against a retaining ring on selective thickness.
- The F/C/D clutch housing and forward one-way clutch outer race are connected, due to friction.

FORWARD ONE-WAY CLUTCH





The LA4A-EL transaxle has a forward one-way clutch that connects these components:
- The forward clutch
- The LOW-INT: Low-intermediate sun gear

The friction plates of the forward clutch with tang teeth are connected to the outer race of the one-way clutch.
The forward one-way clutch transmits torque during drive operation in 1GR, 2GR and 3GR.
This one-way clutch also transmits torque with the coasting clutch during drive and coast operation in 1GR (D-O/D OFF switch OFF), 2GR (D-O/D OFF switch OFF) and 3GR (D-O/D OFF switch OFF).

FORWARD ONE-WAY CLUTCH HOLDING ACTION
- The outer race rotates when the forward clutch is applied.
- The outer race contacts the assembly of sprags, and wedging them between the outer and inner races.
- The wedging action causes the outer race and LOW-INT sun gear which is a part of the inner race to be connected.

COASTING CLUTCH





The LA4A-EL transaxle has a coasting clutch that connects these components for 1GR (D-O/D OFF switch ON, 1 range), 2GR (D-O/D OFF switch ON, 2, 1, range) and 3GR (D-O/D OFF switch ON) operation.
- The F/C/D: Forward/Coasting/Direct clutch cylinder
- The LOW-INT: Low-intermediate sun gear

The turbine shaft is connected to the F/C/D clutch cylinder with spline teeth.
The coasting clutch hub is part of the forward one-way clutch and is LOW-INT Low-intermediate sun gear component.

COASTING CLUTCH APPLY
- Fluid in the Coasting Clutch (CCL) circuit pushes the clutch piston against returning spring force.
- The piston pushes the coasting clutch plates against the forward clutch plates (forward clutch applied).
- The F/C/D clutch cylinder and coasting clutch are connected due to friction.
- The coasting clutch hub is directly connected to the LOW-INT sun gear.

LOW/REVERSE CLUTCH





The LA4A-EL transaxle has a low/reverse clutch that allows the case to hold the Reverse/fourth (REV/4GR) carrier and Low-intermediate (LOW-INT) ring gear stationary in the R position and the 1 range/1GR.
The steel plates of the low/reverse clutch is connected to the transaxle case, by the tang teeth.
The low/reverse friction plates are splined to the REV/4GR carrier.

LOW/REVERSE CLUTCH APPLY
- Fluid in the Reverse or Low (R or L) circuit pushes the clutch piston against returning spring force.
- The clutch piston pushes the low/reverse clutch plates against the outer race of the low one-way clutch. One of the clutch plates has a selective thickness.
- The transaxle case and the LOW-INT ring gear and REV/4GR carrier are connected, due to friction.

LOW ONE-WAY CLUTCH





The LA4A-EL transaxle has a low one-way clutch that allows the case to hold the Reverse/fourth (REV/4GR) carrier, which is splined to the Low-Intermediate (LOW-INT) ring gear. Both are held stationary during drive operation, in 1GR.

The outer race of the clutch connects to the transaxle case with lug teeth, and the inner race connects to the REV/4GR carrier with lug teeth.

LOW ONE-WAY CLUTCH HOLDING ACTION
- The inner race begins to rotate with the REV/4GR carrier which is splined to the LOW-INT ring gear.
- The inner race contacts the assembly of rollers, and wedging them between the outer and inner races.
- The wedging action allows the transaxle case to hold the REV/4GR carrier stationary which is splined to the LOW-INT ring gear.

PLANETARY GEARSETS





The LA4A-EL transaxle has two planetary gearsets labeled as Low-Intermediate (LOW-INT) and Reverse/fourth (REV/4GR). There is also a third gearset to be discussed in the final drive section.
The gearsets provide operation in reverse and four forward speeds using the following parts:
- LOW-INT sun gear
- LOW-INT carrier and REV/4GR ring gear (splined together)
- LOW-INT ring gear and REV/4GR carrier (splined together)
- REV/4GR sun gear
The turbine shaft rotates the LOW-INT sun gear as a driving member through the forward and forward one-way clutches during drive operation only, as well as through the coasting clutch during both drive and coast operation.
The turbine shaft rotates the LOW-INT ring gear and REV/4GR carrier as a driving member through the direct clutch.
The case holds the LOW-INT ring gear and REV/4GR carrier through the low one-way clutch during drive operation only, as well as through the low/reverse clutch during both drive and coast operation. The turbine shaft rotates the REV/4GR sun gear as a driving member through the reverse clutch.
The case holds the REV/4GR sun gear stationary through the 2/4 band.
The LOW-INT carrier and REV/4GR ring gear is always the driven member and is connected to the drive sprocket.

CHAIN DRIVE





The LA4A-EL transaxle has a chain drive to transfer torque from the planetary gearsets to the final drive.
The parts of the chain drive are as follows:
- A drive sprocket, part of the Reverse/fourth (REV/4GR) ring gear
- A driven sprocket component with the final drive sun gear and parking gear and driven sprocket
- A silent-type drive chain

PARKING LOCK





The driven sprocket component has a park gear that has lugs to allow the operation of the parking lock. The parking lock prevents the vehicle wheels from rotating by allowing the transaxle case to hold the driven sprocket component stationary.
When the manual control shaft is rotated to the P position, the parking lock works as follows:
- A cam actuator connected to the manual control shaft rotates, pushing a spring.
- The spring pushes another cam, which rotates to push the parking pawl into alignment between the lugs of the park gear.
- The parking pawl connected to the transaxle case holds the park gear from rotating.

FINAL DRIVE





The LA4A-EL transaxle has a planetary gearset to provide a final drive ratio from the drive chain to the differential.
The final drive parts consist of:
- A sun gear: part of the driven sprocket component
- A ring gear: connected to the converter housing
- A carrier component: which is part of the differential case
During all transaxle operation, final drive sun gear is the driving member. With the ring gear always stationary, the action of the planetary pinions causes the carrier to rotate as the driven member.

DIFFERENTIAL





The LA4A-EL transaxle has a differential component to allow the drive axles and wheels to rotate at different speeds during cornering maneuvers. The parts of the differential are as follows:
- A differential case with final drive carrier
- Two pinion gears supported by a pinion shaft
- A pinion shaft supported by the differential case
- Two side gears supported by the differential case and drive axles
- A speedometer drive gear mounted on the differential case

The differential uses an open-type design that provides operation in the following stages:
- Both drive axles rotate with transmitted torque at the same speed when the vehicle is moving in a straight path.
- Each drive axle rotates with transmitted torque at a different speed when the vehicle is cornering.
- When one drive axle is stationary, the other axle rotates with transmitted torque.