POWERTRAIN OPERATION


BUE051700000A05

Component Descriptions

Component

Function

Forward clutch
Transmits rotation of reverse and forward drum to small sun gear
Coasting clutch
Transmits rotation of reverse and forward drum to small sun gear (for engine braking)
3-4 clutch
Transmits rotation of 3-4 clutch drum to planetary carrier
Reverse clutch
Transmits rotation of reverse and forward drum to large sun gear
2-4 brake band
Prevents rotation of 2-4 brake drum and prevents rotation of large sun gear
Low and reverse brake
Prevents rotation of low and reverse brake hub
One-way clutch 1
Transmits rotation of reverse and forward drum to small sun gear during driving only
One-way clutch 2
Locks clockwise rotation of planetary carrier

Note
• All rotations are viewed from the oil pump.

.

1
Reverse clutch
2
2-4 brake band
3
One-way clutch 2
4
Low and reverse brake
5
Long pinion gear
6
Short pinion gear
7
3-4 clutch
8
Output gear
9
Forward clutch
10
Coasting clutch
11
One-way clutch 1
12
Large sun gear
13
Small sun gear
14
Internal gear

Forward Clutch

• When hydraulic pressure acts upon the clutch piston, the drive plates and the driven plates are pressed tightly together, and the rotation of the turbine shaft is transmitted via the reverse and forward drum and one-way clutch 1 to the small sun gear.

Coasting Clutch

• When hydraulic pressure acts on the clutch piston, the drive plates and the driven plates are pressed tightly together, and the rotation of the turbine shaft is transmitted via the reverse and forward drum, coasting clutch drum and one-way clutch inner race to the small sun gear.

• Then when the coasting clutch engages, the forward clutch is engaged and the one-way clutch 1 becomes locked.

• The return spring is common for the forward clutch and the coasting clutch.

.

1
Reverse and forward drum
2
Turbine shaft
3
One-way clutch 1
4
Coasting clutch
5
Forward clutch
6
Small sun gear
7
Driven prate
8
Drive prate
9
One-way clutch outer race
10
Coasting clutch drum
11
Coasting clutch piston
12
One-way clutch inner race
13
All rotations are viewed the oil pump

3-4 Clutch

• When hydraulic pressure acts on the clutch piston, the drive plates and the driven plates are pressed tightly together, and the rotation of the turbine shaft is transmitted via the 3-4 clutch drum and the carrier hub to the planetary carrier.

Reverse Clutch

•  When hydraulic pressure acts on the clutch piston, the drive plates and the driven plates are pressed tightly together, and the rotation of the turbine shaft is transmitted via the reverse and forward drum and the 2-4 brake drum to the large sun gear. A diaphragm spring is used for return spring.

.

1
Reverse and forward drum
2
Reverse clutch
3
2-4 brake drum
4
Planetary carrier
5
3-4 clutch
6
Large sun gear
7
Turbine shaft
8
Reverse clutch drum
9
Driven prate
10
Drive prate
11
3-4 clutch piston
12
All rotations are viewed the oil pump

2-4 Brake

• When hydraulic pressure is applied between the servo retainer and the servo piston (brake band engagement side), the servo piston overcomes the spring force and acts on the brake band, thus locking the 2-4 brake drum.

• When hydraulic pressure is applied between the servo piston and the transaxle case (brake band disengagement side), the servo piston is pressed toward the servo retainer side. The brake band expands by its own spring force, thus releasing the 2-4 brake drum.

• When hydraulic pressure is applied simultaneously between the servo retainer and the servo piston and between the servo piston and transaxle case, the servo piston is pressed to the servo retainer side as a result of the difference of the surface area between the two, thus releasing the 2-4 brake drum.

Low and Reverse Brake

• When hydraulic pressure acts on the brake piston, the drive plates and the driven plates are pressed tightly together, and the transaxle case and the low and reverse brake inner race are connected. The rotation of the planetary carrier is locked when the low and reverse brake is activated.

.

1
2-4 brake band
2
2-4 brake drum
3
Low and reverse brake
4
Planetary carrier
5
Inner race
6
Large sun gear
7
One-way clutch inner race
8
One-way clutch outer race
9
Drive prate
10
Driven prate
11
Low and reverse brake piston
12
All rotations are viewed the oil pump

One-way Clutch 1

• If the rotation speed of the one-way clutch outer race is faster than that of the one-way clutch inner race, the sprags enter between the two races and lock them. Consequently, the driving force is transferred to the small sun gear via one-way clutch 1. In 4GR, the one-way clutch 1 runs idle and does not transfer the driving force because the rotation speed of the one-way clutch inner race is faster.

One-way Clutch 2

• The one-way clutch inner race rotates counterclockwise freely. However, in the roller type, if the inner race tries to rotate clockwise, the rollers move to the shallower grooves and enter between the races. In either case, the one-way clutch inner race is locked. In other words, one-way clutch 2 locks the clockwise rotation of the planetary carrier and the pinion gear.

.

1
Planetary carrier
2
Inner race
3
One-way clutch 2
4
One-way clutch 4
5
Outer race
6
Small sun gear
7
One-way clutch inner race
8
One-way clutch outer race
9
All rotations are viewed the oil pump