Service Manuals, User Guides, Schematic Diagrams or docs for : . Car Manuals Subaru Impreza 2001-2002.2004-2007 Approved Subaru Impreza 2004 WRX STi 08. MECHANISM AND FUNCTION 33. AUTOMATIC TRANSMISSION 09. Gear Train
<< Back | HomeMost service manuals and schematics are PDF files, so You will need Adobre Acrobat Reader to view : Acrobat Download Some of the files are DjVu format. Readers and resources available here : DjVu Resources
For the compressed files, most common are zip and rar. Please, extract files with Your favorite compression software ( WinZip, WinRAR ... ) before viewing. If a document has multiple parts, You should download all, before extracting.
Good luck. Repair on Your own risk. Make sure You know what You are doing.
Image preview - the first page of the document
>> Download 09. Gear Train documenatation <<
Text preview - extract from the document
W1860BE.book Page 18 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
9. Gear Train
A: CONSTRUCTION
The gear train consists of two sets of planetary gears, three sets of multi-plate clutches, two sets of
multi-plate brakes and one set of one-way clutch.
(8)
(4) (6)
(3) (14) (5) (7)
(2)
(9)
(10)
(1)
(17)
(11)
(15)
(13) (12)
(16)
AT-00474
(1) Input shaft (7) One-way clutch (13) Rear sun gear
(2) High clutch (operates in 3rd and 4th speeds) (8) Free/locked (14) Front planetary carrier
(3) Reverse clutch (operates while moving in reverse) (9) Rear planetary carrier (15) Front internal gear
(4) 2-4 brake (10) MPT models: reduction (16) Front pinion gear
drive shaft
VTD Models: intermediate
shaft
(5) Low clutch (11) Rear internal gear (17) Front sun gear
(6) Low & reverse brake (12) Rear pinion gear
4AT-18
W1860BE.book Page 19 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
B: OPERATION
1. OPERATION TABLE
Low & One-
Reverse 2-4 High Low
reverse way
clutch brake clutch clutch
brake clutch
P
R
N
1ST
2ND
D
3RD
4TH
1ST
Selector lever operation
2ND
3
3RD
4TH
1ST
2ND
2
3RD
4TH
1ST
2ND
1
3RD
4TH
AT-00868
4AT-19
W1860BE.book Page 20 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
2. N RANGE
Since the rear sun gear and the high clutch drum are in mesh with the input shaft, they rotate to-
gether with the input shaft.
The high clutch drum does not transmit the torque to the planetary unit since the reverse clutch and
the high clutch are not engaged.
The torque of the rear sun gear is transmitted to the rear internal gear through the pinion gear.
However, the torque of the rear sun gear is not transmitted to the rear planetary carrier since the
low clutch is disengaged and, therefore, the rear internal gear is freewheeling.
As a result, the torque of the input shaft is not transmitted to the reduction drive shaft*.
*: MPT models only. VTD models are equipped with an intermediate shaft.
Operating condition of components Power flow (in acceleration)
All clutches and brakes : disengaged
Input shaft
Rear sun gear
Rear pinion gear
Rear internal gear
Low clutch (free)
AT-00476
4AT-20
W1860BE.book Page 21 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
(8)
(4) (6)
(3) (5) (7)
(2)
(9)
(10)
(1)
(12)
(13) (11)
: (14)
: (15)
: (16)
: (17)
AT-00477
(1) Input shaft (7) One-way clutch (13) Rear sun gear
(2) High clutch (8) No effect (14) Input
(3) Reverse clutch (9) Rear planetary carrier (15) Output
(4) 2-4 brake (10) MPT models: reduction drive shaft (16) Lock
VTD Models: intermediate shaft
(5) Low clutch (11) Rear internal gear (17) Planetary gear components in-
volved in power transmission
(6) Low & reverse brake (12) Rear pinion gear
4AT-21
W1860BE.book Page 22 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
3. P RANGE
All the clutches and brakes are free, just as in the N range. The parking pawl engages with the park-
ing gear which forms an integral part of the reduction drive gear, preventing the gear from rotating.
Operating condition of components Power flow (in acceleration)
All clutches and brakes : disengaged
Input shaft
Rear sun gear
Rear pinion gear
Rear internal gear
Low clutch (free)
AT-00476
4AT-22
W1860BE.book Page 23 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
(8)
(4) (6)
(3) (5) (7)
(2)
(9)
(10)
(1)
(12)
(13) (11)
: (14)
: (15)
: (16)
: (17)
AT-00477
(1) Input shaft (7) One-way clutch (13) Rear sun gear
(2) High clutch (8) No effect (14) Input
(3) Reverse clutch (9) Rear planetary carrier (15) Output
(4) 2-4 brake (10) MPT models: reduction drive shaft (16) Lock
VTD Models: intermediate shaft
(5) Low clutch (11) Rear internal gear (17) Planetary gear components in-
volved in power transmission
(6) Low & reverse brake (12) Rear pinion gear
4AT-23
W1860BE.book Page 24 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
4. 1ST SPEED GEAR OF D OR 3 RANGE (D1, 31)
When the 1st gear is selected in the D or 3 range, only the low clutch is engaged. In this state, the
rear internal gear attempts to rotate counterclockwise but it is impossible by the action of the one-
way clutch which locks the internal gear to the transmission case. As a result, rotation of the rear
sun gear causes the pinion gears to rotate around the sun gear. This causes the planetary carrier
to rotate. In this way, rotation of the input shaft is transmitted to the reduction drive shaft* after being
subjected to speed reduction by the planetary gear train.
On the other hand, the rear internal gear rotates clockwise if the reverse driving force is applied to
it by the reduction drive shaft* during coasting. This clockwise rotation of the internal gear causes
the one-way clutch to freewheel. Since the power path between the reduction drive shaft* and the
input shaft is lost as a result, no engine braking effect is available.
*: MPT models only. VTD models are equipped with an intermediate shaft.
Operating condition of components
Low clutch : engaged
One-way clutch : locked
Power flow (in acceleration)
MPT models VTD models
Input shaft
Input shaft
Rear sun gear
Rear sun gear
Rear pinion gear
Rear pinion gear
Rear planetary carrier
Rear planetary carrier
Intermediate shaft
Reduction gear
Center differential assembly
Drive pinion Transfer clutch
Reduction gear LSD Rear drive shaft
Front differential Rear differential
Drive pinion Rear differential
AT-00480 Front differential AT-00713
4AT-24
W1860BE.book Page 25 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
(8)
(4) (6)
(3) (5) (7)
(2)
(9)
(10)
(1)
(13) (11)
(12)
: (14)
: (15)
: (16)
: (17)
AT-00481
(1) Input shaft (7) One-way clutch (13) Rear sun gear
(2) High clutch (8) Locked (14) Input
(3) Reverse clutch (9) Rear planetary carrier (15) Output
(4) 2-4 brake (10) MPT models: reduction drive shaft (16) Locked
VTD Models: intermediate shaft
(5) Low clutch (11) Rear internal gear (17) Planetary gear components in-
volved in power transmission
(6) Low & reverse brake (12) Rear pinion gear
4AT-25
W1860BE.book Page 26 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
5. 2ND SPEED GEAR IN D, 3, 2 RANGE (D2, 32, 22)
When the 2nd gear is selected in D, 3, or 2 range, the 2-4 brake and the low clutch are engaged.
The front sun gear is now locked to the transmission case due to engagement of the 2-4 brake. In
this state, the torque of the rear sun gear is transmitted to the rear internal gear through the path of
the front internal gear, front pinion gears, low clutch drum and low clutch. At this time, the one-way
clutch is freewheeling since the low clutch drum is rotating clockwise.
In this power flow configuration, the rear pinion gears are rotated by the rear internal gear at a speed
faster than that available from the configuration for the 1st gear, so the rotation speed of the reduc-
tion drive shaft* is higher than that of the 1st gear.
Since the drive power is transmitted without passing through the one-way clutch in the 2nd gear, the
backward driving force from the wheels is transmitted through the reduction drive shaft* to the input
shaft; this makes the engine braking effect available.
*: MPT models only. VTD models are equipped with an intermediate shaft.
Operating condition of components
Low clutch : engaged
2-4 brake : engaged
Power flow (in acceleration)
MPT models VTD models
Input shaft Input shaft
Rear sun gear Rear sun gear
Rear pinion gear Rear pinion gear
Rear planetary carrier Rear planetary carrier
Reduction drive shaft Front internal Intermediate shaft Front internal
gear gear
Center differential
assembly
Reduction drive Transfer clutch Front pinion Front pinion
gear gear gear
Front differential Rear differential Low clutch Reduction drive Rear drive shaft Low clutch
gear
Rear internal Rear internal
gear Front differential Rear differential gear
AT-00482 AT-00714
4AT-26
W1860BE.book Page 27 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
(8)
(4) (6)
(3) (5) (7)
(2)
(9)
(10)
(1)
(16)
(14)
(11)
(15) (12)
(13)
: (17)
: (18)
: (19)
: (20)
AT-00483
(1) Input shaft (8) Free (15) Front pinion gear
(2) High clutch (9) Rear planetary carrier (16) Front sun gear
(3) Reverse clutch (10) MPT models: reduction drive shaft (17) Input
VTD Models: intermediate shaft
(4) 2-4 brake (11) Rear internal gear (18) Output
(5) Low clutch (12) Rear pinion gear (19) Locked
(6) Low & reverse clutch (13) Rear sun gear (20) Planetary gear components in-
volved in power transmission
(7) One-way clutch (14) Front internal gear
4AT-27
W1860BE.book Page 28 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
6. 3RD SPEED GEAR IN D OR 3 RANGE (D3, 33)
When the 3rd gear is selected in the D or 3 range, the low clutch and the high clutch are engaged.
The engaged high clutch rotates through its drum the front planetary carrier, and rotation of the car-
rier is transmitted to the rear internal gear through the engaged low clutch. In this power flow con-
figuration, the rear sun gear and the rear internal gear rotate at the same speed since the rear pinion
gears are solid on their axes and the whole planetary gear train rotates as a unit at the same speed
as its sun gear. As a result, the input shaft and the reduction drive shaft* rotate at the same speed.
In the 3rd gear, the one-way clutch is freewheeling because the low clutch is rotating clockwise.
Since the drive power is transmitted without passing through the one-way clutch, the backward driv-
ing force from the wheels is transmitted through the reduction drive shaft* to the input shaft; this
makes the engine braking effect available.
*: MPT models only. VTD models are equipped with an intermediate shaft.
4AT-28
W1860BE.book Page 29 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
Operating condition of components
High clutch : engaged
Low clutch : engaged
Power flow (in acceleration)
MPT models VTD models
Input shaft
Input shaft
High clutch Rear sun gear
High clutch Rear sun gear
Front planetary carrier
Front planetary carrier
Low clutch
Low clutch
Rear internal gear
Rear internal gear
Rear pinion gear
Rear pinion gear
Rear planetary carrier
Rear planetary carrier
Intermediate shaft
Reduction drive shaft
Center differential assembly
Reduction drive gear Transfer clutch
Reduction drive LSD Rear drive shaft
gear
Front differential Rear differential
Front differential Rear differential
AT-00484 AT-00715
4AT-29
W1860BE.book Page 30 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
(9)
(4) (7)
(5)
(3) (6) (8)
(2)
(10)
(1) (11)
(17)
(16)
(15) (12)
(13)
(14)
: (18)
: (19)
: (20)
: (21)
AT-00485
(1) Input shaft (8) One-way clutch (15) Front internal gear
(2) High clutch (9) Free (16) Front pinion gear
(3) Reverse clutch (10) Rear planetary carrier (17) Front sun gear
(4) 2-4 brake (11) MPT models: reduction drive shaft (18) Input
VTD Models: intermediate shaft
(5) Front planetary carrier (12) Rear internal gear (19) Output
(6) Low clutch (13) Rear pinion gear (20) Locked
(7) Low & reverse brake (14) Rear sun gear (21) Planetary gear components in-
volved in power transmission
4AT-30
W1860BE.book Page 31 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
7. 4TH SPEED GEAR IN D RANGE (D4)
When the 4th gear is selected in the D range, the high clutch and the 2-4 brake are engaged. The
engaged high clutch causes the front planetary carrier to rotate, whereas the engaged 2-4 brake
causes the front sun gear to be locked to the transmission case.
The front planetary carrier rotates at the same speed as the input shaft. The rotation of the front
planetary carrier causes the front pinion gears to revolve around the stationary front sun gear, which
causes the front internal gear to rotate faster than the input shaft.
As a result, the reduction drive shaft* is driven at a higher speed than the input shaft.
In the 4th gear, the one-way clutch is freewheeling because the low clutch is rotating clockwise.
Since the drive power is transmitted without passing through the one-way clutch, the backward driv-
ing force from the wheels is transmitted through the reduction drive shaft* to the input shaft; this
makes the engine braking effect available.
*: MPT models only. VTD models are equipped with an intermediate shaft.
Operating condition of components
2-4 brake : engaged
High clutch : engaged
Power flow (in acceleration)
MPT models VTD models
Input shaft Input shaft
High clutch High clutch
Front planetary carrier
Front planetary carrier
Front pinion gear
Front pinion gear
Front internal gear
Front internal gear
Rear planetary carrier
Rear planetary carrier Intermediate shaft
Reduction drive shaft Center differential assembly
Reduction drive gear Transfer clutch Reduction drive LSD Rear drive shaft
gear
Front differential Rear differential Front differential Rear differential
AT-00486 AT-00716
4AT-31
W1860BE.book Page 32 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
(9)
(4) (7)
(5)
(3) (6) (8)
(2)
(10)
(1)
(11)
(17)
(15) (12)
(14) (13)
(16)
: (18)
: (19)
: (20)
: (21)
AT-00487
(1) Input shaft (8) One-way clutch (15) Front internal gear
(2) High clutch (9) Free (16) Front pinion gear
(3) Reverse clutch (10) Rear planetary carrier (17) Front sun gear
(4) 2-4 brake (11) MPT models: reduction drive shaft (18) Input
VTD Models: intermediate shaft
(5) Front planetary carrier (12) Rear internal gear (19) Output
(6) Low clutch (13) Rear pinion gear (20) Locked
(7) Low & reverse brake (14) Rear sun gear (21) Planetary gear components in-
volved in power transmission
4AT-32
W1860BE.book Page 33 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
8. 1ST SPEED GEAR IN 1 RANGE (11)
When the 1st gear is selected in the 1 range, both the low clutch and the low & reverse brake are
engaged. Although the power flow configuration is the same as that with the 1st gear in the D or 3
range, the one-way clutch produces no freewheeling effect because the low & reverse brake is lock-
ing the rear internal gear always to the transmission case.
During coasting, therefore, the backward driving force from the wheels is transmitted through the
reduction drive gear* to the input shaft. This means, unlike the 1st gear in D or 3 range, that the
engine braking effect is available in this range.
*: MPT models only. VTD models are equipped with an intermediate shaft.
Operating condition of components
Low clutch : engaged
Low & reverse brake : engaged
One-way clutch : no effect
Power flow (in acceleration)
MPT models VTD models
Input shaft
Input shaft
Rear sun gear
Rear sun gear
Rear pinion gear
Rear pinion gear
Rear planetary carrier
Rear planetary carrier
Intermediate shaft
Reduction drive shaft
Center differential assembly
Reduction drive gear Transfer clutch
Reduction drive LSD Rear drive shaft
gear
Front differential Rear differential
Front differential Rear differential
AT-00488 AT-00717
4AT-33
W1860BE.book Page 34 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
(9)
(4) (7)
(5)
(3) (6) (8)
(2)
(10)
(1) (11)
(17) (13)
(15) (14) (12)
(16)
: (18)
: (19)
: (20)
: (21)
AT-00489
(1) Input shaft (8) One-way clutch (15) Front internal gear
(2) High clutch (9) no effect (16) Front pinion gear
(3) Reverse clutch (10) Rear planetary carrier (17) Front sun gear
(4) 2-4 brake (11) MPT models: reduction drive shaft (18) Input
VTD Models: intermediate shaft
(5) Front planetary carrier (12) Rear internal gear (19) Output
(6) Low clutch (13) Rear pinion gear (20) Locked
(7) Low & reverse brake (14) Rear sun gear (21) Planetary gear components in-
volved in power transmission
4AT-34
W1860BE.book Page 35 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
9. R RANGE
When the selector lever is placed in the R position, the reverse clutch and the low & reverse brake
are engaged. The reverse clutch allows the input shaft torque to be transmitted to the front sun gear,
while the low & reverse brake allows the low clutch drum to be interlocked with the transmission
case.
The rotation of the front sun gear causes the front pinion gear to rotate in the opposite direction and
therefore the front internal gear rotates in the same direction.
At this time, the rotation speed transmitted to the front internal gear is reduced through gearing be-
tween the front sun gear and the front pinion gears.
The one-way clutch produces no freewheeling effect because the low & reverse brake is in engage-
ment.
In this range, since the power transmission is made without passing through the one-way clutch, the
driving force from the wheels is transmitted through the reduction drive shaft* to the input shaft; this
makes the engine braking effect available.
*: MPT models only. VTD models are equipped with an intermediate shaft.
Operating condition of components
Reverse clutch : engaged
Low & reverse brake : engaged
Power flow (in acceleration)
MPT models VTD models
Input shaft Input shaft
Reverse clutch
Reverse clutch
Front sun gear
Front sun gear
Front pinion gear
Front pinion gear
Front internal gear
Front internal gear
Rear planetary carrier
Rear planetary carrier
Intermediate shaft
Reduction drive shaft Center differential assembly
Reduction drive gear Transfer clutch Reduction drive LSD Rear drive shaft
gear
Front differential Rear differential Front differential Rear differential
AT-00490 AT-00718
4AT-35
W1860BE.book Page 36 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
(9)
(4) (7)
(3) (6) (8)
(5)
(2)
(10)
(11)
(1)
(14)
(12)
(17) (15) (13)
(16)
: (18)
: (19)
: (20)
: (21)
AT-00491
(1) Input shaft (8) One-way clutch (15) Front internal gear
(2) High clutch (9) no effect (16) Front pinion gear
(3) Reverse clutch (10) Rear planetary carrier (17) Front sun gear
(4) 2-4 brake (11) MPT models: reduction drive shaft (18) Input
VTD Models: intermediate shaft
(5) Front planetary carrier (12) Rear internal gear (19) Output
(6) Low clutch (13) Rear pinion gear (20) Locked
(7) Low & reverse brake (14) Rear sun gear (21) Planetary gear components in-
volved in power transmission
4AT-36
W1860BE.book Page 37 Tuesday, January 28, 2003 11:01 PM
GEAR TRAIN
AUTOMATIC TRANSMISSION
MEMO
4AT-37
◦ Jabse Service Manual Search 2026 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo