Third Gear

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Fig 1: Identifying Third Gear Planetary Operation

Courtesy of MAZDA MOTORS CORP.

THIRD GEAR ROTATION SPEED REFERENCE

Planetary gear	Rear
Internal gear	N_R (input)
Planetary carrier	N_C (output)
Sun gear	N_S (input)

Here we have the result of N_R =N_S .
Suppose the gear ratio in third gear is i₃ ,

Fig 2: Identifying 3rd Gear Ratio Formula (1 Of 2)
Courtesy of MAZDA MOTORS CORP.
From the result of N_R =N_S in formula (1), the relation between the gear ratio in third gear and the rotation speed of the rear planetary gear set is indicated in the formula below.
(Z_RR +Z_SR ) N_C = (Z_RR +Z_SR ) N_R
Therefore,

Fig 3: Identifying 3rd Gear Ratio Formula (2 Of 2)
Courtesy of MAZDA MOTORS CORP.
As a result, the gear ratio in third gear is 1.000.