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AT-18
A/T CONTROL SYSTEM
Revision: November 20092006 QX56
Cross-Sectional View (4WD models)ECS00CDU
1. Front planetary gear2. Mid planetary gear 3. Rear planetary gear
4. Direct clutch 5. High and low reverse clutch 6. Reverse brake
7. Drum support 8. Forward brake 9. Low coast brake
10. Input shaft 11. Torque converter 12. Oil pump
13. Front brake 14. 3rd one-way clutch 15. Input clutch
16. 1st one-way clutch 17. Control valve with TCM 18. Forward one-way clutch
19. Adapter case 20. Output shaft
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A/T CONTROL SYSTEMAT-19
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Revision: November 2009 2006 QX56
Shift MechanismECS00CDV
The automatic transmission uses compact triple planetary gear systems to improve power-transmission effi-
ciency, simplify construction and reduce weight.
It also employs an optimum shift control and super wide gear ratios. They improve starting performance and
acceleration during medium and high-speed operation.
CONSTRUCTION
FUNCTION OF CLUTCH AND BRAKE
1. Front brake 2. Input clutch3. Direct clutch
4. High and low reverse clutch 5. Reverse brake6. Forward brake
7. Low coast brake 8. 1st one-way clutch9. Forward one-way clutch
10. 3rd one-way clutch 11. Front sun gear12. Input shaft
13. Mid internal gear 14. Front internal gear15. Rear carrier
16. Rear sun gear 17. Mid sun gear18. Front carrier
19. Mid carrier 20. Rear internal gear21. Output shaft
22. Parking gear 23. Parking pawl
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Name of the PartAbbreviation Function
Front brake (1) FR/B Fastens the front sun gear (11).
Input clutch (2) I/CConnects the input shaft (12), the front internal gear (14) and the mid internal
gear (13).
Direct clutch (3) D/C Connects the rear carrier (15) and the rear sun gear (16).
High and low reverse clutch (4) HLR/C Connects the mid sun gear (17) and the rear sun gear (16).
Reverse brake (5) R/B Fastens the rear carrier (15).
Forward brake (6) Fwd/B Fastens the mid sun gear (17).
Low coast brake (7) LC/B Fastens the mid sun gear (17).
1st one-way clutch (8) 1st OWCAllows the rear sun gear (16) to turn freely forward relative to the mid sun gear
(17) but fastens it for reverse rotation.
Forward one-way clutch (9) Fwd OWCAllows the mid sun gear (17) to turn freely in the forward direction but fastens it
for reverse rotation.
3rd one-way clutch (10) 3rd OWCAllows the front sun gear (11) to turn freely in the forward direction but fastens
it for reverse rotation.
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AT-20
A/T CONTROL SYSTEM
Revision: November 20092006 QX56
CLUTCH AND BAND CHART
—Operates
—Operates during “progressive ” acceleration.
—Operates and effects power transmission while coasting.
—Line pressure is applied but does not affect power transmission.
—Operates under conditions shown in HLR/C Operating Condition
— Operates under conditions shown in LC/B Operating Condition. Delay control is applied during D (4,3,2,1) N shift.
Shift position I/C HLR/C D/C R/B FR/B LC/B Fwd/B
1st
OWC Fwd
OWC 3rd
OWC Remarks
P PARK POSITION
R REVERSE
POSITION
N NEUTRAL POSI-
TION
D 1st
Automatic shift
1 ⇔ 2⇔ 3⇔ 4⇔ 5
2nd
3rd4th
5th
1st
4 2nd
Automatic shift
3rd 1
⇔ 2⇔ 3⇔ 4
4th
3 1st
Automatic shift1⇔ 2⇔ 3⇐ 4
2nd
3rd 4th
2 1st
Automatic shift1⇔ 2⇐ 3⇐ 4
2nd
3rd4th
1 1st
Locks (held sta-tionary in 1st
gear)
1 ⇐ 2⇐ 3⇐ 4
2nd
3rd
4th
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A/T CONTROL SYSTEMAT-21
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POWER TRANSMISSION
“N” Position
Since both the forward brake and the reverse brake are released, torque from the input shaft drive is not trans-
mitted to the output shaft.
“P” Position
The same as for the “N” position, both the forward brake and the reverse brake are released, so torque
from the input shaft drive is not transmitted to the output shaft.
The parking pawl linked with the select lever meshes with the parking gear and fastens the output shaft
mechanically.
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1. Front brake 2. Input clutch3. Direct clutch
4. High and low reverse clutch 5. Reverse brake 6. Forward brake
7. Low coast brake 8. 1st one-way clutch9. Forward one-way clutch
10. 3rd one-way clutch 11. Front sun gear12. Input shaft
13. Mid internal gear 14. Front internal gear15. Rear carrier
16. Rear sun gear 17. Mid sun gear18. Front carrier
19. Mid carrier 20. Rear internal gear21. Output shaft
22. Parking gear 23. Parking pawl
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AT-22
A/T CONTROL SYSTEM
Revision: November 20092006 QX56
“D”, “4”, “3”, “2” Positions 1st Gear
The forward brake and the forward one-way clutch regulate reverse rotation of the mid sun gear.
The 1st one-way clutch regulates reverse rotation of the rear sun gear.
The 3rd one-way clutch regulates reverse rotation of the front sun gear.
During deceleration, the mid sun gear turns forward, so the forward one-way clutch idles and the engine
brake is not activated.
1. Front brake2. Input clutch 3. Direct clutch
4. High and low reverse clutch 5. Reverse brake 6. Forward brake
7. Low coast brake 8. 1st one-way clutch 9. Forward one-way clutch
10. 3rd one-way clutch 11. Front sun gear 12. Input shaft
13. Mid internal gear 14. Front internal gear 15. Rear carrier
16. Rear sun gear 17. Mid sun gear 18. Front carrier
19. Mid carrier 20. Rear internal gear 21. Output shaft
22. Parking gear 23. Parking pawl
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A/T CONTROL SYSTEMAT-23
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“1 ” Position 1st Gear
The front brake fastens the front sun gear.
The forward brake and the forward one-way clutch regulate reverse rotation of the mid sun gear.
High and low reverse clutch connects the rear sun gear and the mid sun gear.
The low coast brake fastens the mid sun gear.
During deceleration, the low coast brake regulates forward rotation of the mid sun gear and the engine
brake functions.
1. Front brake2. Input clutch3. Direct clutch
4. High and low reverse clutch 5. Reverse brake 6. Forward brake
7. Low coast brake 8. 1st one-way clutch9. Forward one-way clutch
10. 3rd one-way clutch 11. Front sun gear12. Input shaft
13. Mid internal gear 14. Front internal gear15. Rear carrier
16. Rear sun gear 17. Mid sun gear18. Front carrier
19. Mid carrier 20. Rear internal gear21. Output shaft
22. Parking gear 23. Parking pawl
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AT-24
A/T CONTROL SYSTEM
Revision: November 20092006 QX56
“D”, “4”, “3” Positions 2nd Gear
The forward brake and the forward one-way clutch regulate reverse rotation of the mid sun gear.
The 3rd one-way clutch regulates reverse rotation of the front sun gear.
The direct clutch is coupled and the rear carrier and rear sun gear are connected.
During deceleration, the mid sun gear turns forward, so the forward one-way clutch idles and engine
brake is not activated.
1. Front brake2. Input clutch 3. Direct clutch
4. High and low reverse clutch 5. Reverse brake 6. Forward brake
7. Low coast brake 8. 1st one-way clutch 9. Forward one-way clutch
10. 3rd one-way clutch 11. Front sun gear 12. Input shaft
13. Mid internal gear 14. Front internal gear 15. Rear carrier
16. Rear sun gear 17. Mid sun gear 18. Front carrier
19. Mid carrier 20. Rear internal gear 21. Output shaft
22. Parking gear 23. Parking pawl
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A/T CONTROL SYSTEMAT-25
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Revision: November 2009 2006 QX56
“2”, “1” Positions 2nd Gear
The front brake fastens the front sun gear.
The forward brake and the forward one-way clutch regulate reverse rotation of the mid sun gear.
The direct clutch is coupled, and the rear carrier and rear sun gear are connected.
The low coast brake fastens the mid sun gear.
During deceleration, the low coast brake regulates forward rotation of the mid sun gear and the engine
brake functions.
1. Front brake2. Input clutch3. Direct clutch
4. High and low reverse clutch 5. Reverse brake 6. Forward brake
7. Low coast brake 8. 1st one-way clutch9. Forward one-way clutch
10. 3rd one-way clutch 11. Front sun gear12. Input shaft
13. Mid internal gear 14. Front internal gear15. Rear carrier
16. Rear sun gear 17. Mid sun gear18. Front carrier
19. Mid carrier 20. Rear internal gear21. Output shaft
22. Parking gear 23. Parking pawl
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