Mazda 5. Manual - part 26

05–17–24

AUTOMATIC TRANSAXLE 

End Of Sie

PLANETARY GEAR STRUCTURE

B3E051701030A21

• The front planetary gear is integrated with the one-way clutch outer race and engaged with the drive plate of 

the low and reverse brake.
Because of this, when the front planetary gear rotates, the one-way clutch outer race and the drive plate of the 
low and reverse brake also rotate together.

• The front sun gear is installed inside of the front pinion gears, and the front internal gear is installed outside of 

the front pinion gears. The front sun gear is engaged with the forward clutch hub, and the front internal gear is 
engaged with the rear planetary carrier.

• The rear planetary gear and the rear pinion gear have the rear sun gear installed inside and the rear internal 

gear outside. The rear sun gear is engaged with the turbine shaft via the 2-4 brake drum, and the rear internal 
gear is engaged with the primary gear via the front planetary carrier.

.

End Of Sie

PLANETARY GEAR OPERATION

B3E051701030A22

• The planetary gear works as a transaxle when the sun gear and the internal gear are engaged.

• The sun gear, installed inside of the pinion gears, and the internal gear, installed outside of the pinion gears, 

are engaged with their respective gears.

9

8

7

5

4

3

6

1

2

B3E0517A005

1

Rear internal gear

2

Front internal gear

3

Low and reverse brake

4

Rear planetary carrier

5

Rear pinion gear

6

Rear sun gear

7

Front pinion gear

8

Front planetary carrier

9

Front sun gear

AUTOMATIC TRANSAXLE 

05–17–25

05

The sun gear and the internal gear rotate on the 
center of the planetary gear.

.

• The pinion gears turn in the following two ways:

— On their own centers (rotation)

— On the center of the planetary gear 

(revolution)

.

Gear ratio of each range

• The relation between each element of the planetary gear set and the rotation speed is generally indicated in 

the formula below.
(Z

R

+Z

S

) N

C

=Z

R

N

R

+Z

S

N

S

: formula (1)

"

 



!

B3E0517A006

1

Sun gear

2

Internal gear

3

Planetary carrier

4

Pinion gear

1

2

B3E0517A007

1

Rotation

2

Revolution

05–17–26

AUTOMATIC TRANSAXLE 

In this formula Z stands for the number of teeth, N 
stands for the rotation speed, and R, S, C stand 
for each gear element (refer to the table below).

.

Number of teeth and symbol of each gear

First gear

.

Gear rotation speed

• Suppose gear ratio in first gear is i

1

,

i

1

=N

S

/N

C

• From the result N

R

=0 in formula (1), the relation between the gear ratio in first gear and the rotation speed of 

the planetary gear set is indicated in the formula below.
(Z

RF

+Z

SF

) N

C

=Z

SF

N

S

Therefore,
i

1

=N

S

/N

C

= (Z

RF

+Z

SF

) /Z

SF

= (89+49) /49=2.8163

"

 



!

B3E0517A006

1

Sun gear

2

Internal gear

3

Planetary carrier

4

Pinion gear

Planetary gear unit

Planetary gear 

element

Number of teeth

Unit identification symbol

Gear element

Unit

Front

Internal gear

89

R

F

Planetary carrier 
(part of pinion gear)

20

C

F

Sun gear

49

S

F

Rear

Internal gear

98

R

R

Planetary carrier 
(part of pinion gear)

30

C

R

Sun gear

37

S

R

1

Front planetary gear

2

Sun gear N

S

 (input)

3

Internal gear (fix)

4

Planetary carrier N

C

 (output)

5

Pinion gear

Planetary gear unit

Front

Internal gear

0 (fix)

Planetary carrier

N

C

 (output)

Sun gear

N

S

 (input)

5

4

3

1

2

B3E0517A008

AUTOMATIC TRANSAXLE 

05–17–27

05

As a result, the gear ratio in first gear is 2.816.

Second gear

Gear rotation speed

Note

• The front internal gear and the rear planetary carrier are integrated.

• The front planetary carrier and the rear internal gear rotate at the same speed.

• Suppose gear ratio in second gear is i

2

,

i

2

=N

S

/N

R

• From formula (1), the relation between the gear ratio in second gear and the rotation speeds of the front and 

the rear planetary gar sets is indicated in formulas (2) and (3).
(Z

RF

+Z

SF

) N

R

=Z

RF

N

C

+Z

SF

N

S

: (2) (Front planetary gear set)

(Z

RR

+Z

SR

) N

C

=Z

RR

N

R

+Z

SR

N

S

: (3) (Rear planetary gear set)

• From the result N

S

=0 in formula (3).

N

C

= (Z

RR

/ (Z

RR

+Z

SR

)) N

R

: (4)

• Here we substitute formula (4) in formula (2).

Z

SR

N

S

= (((Z

RR

+Z

SR

) (Z

RF

+Z

SF

) –Z

RF

Z

RR

) / (Z

RR

+Z

SR

)) N

R

Therefore,
i

2

=N

S

/N

R

= (((Z

RR

+Z

SR

) (Z

RF

+Z

SF

) –Z

RF

Z

RR

) / (Z

SF

 (Z

RR

+Z

SR

))) N

R

= ((98+37)(84+49) –8998) / (49 (98+37)) 

=1.4978
As a result, the gear ratio in second gear is 1.497.

1

9

8

5

4

3

6

2

6

7

B3E0517A009

1

Front planetary gear

2

Rear planetary gear

3

Sun gear N

S

 (input)

4

Internal gear N

R

5

Planetary carrier N

C

 (output)

6

Pinion gear

7

Sun gear N

S

 (fix)

8

Internal gear N

R

 (output)

9

Planetary carrier N

C

Planetary gear

Front

Rear

Internal gear

N

R

N

R

 (output)

Planetary carrier

N

C

 (output)

N

C

Sun gear

N

S

 (input)

N

S

 (fix)