2

When the gear selector is placed in the 2−position, the second coast
brake (B1) is applied by way of the manual valve. When the second
coast brake is applied, it holds the sun gear from rotating in either
direction. Power flow is the same with the selector in 2," as when the
selector is in D" because the second coast brake is parallel to the
second brake and No. 1 one−way clutch.

However, when the transmission is being driven by the wheels on
deceleration, the force from the output shaft is transmitted to the front
carrier, causing the front planetary pinion gears to revolve clockwise
around the sun gear. Since the sun gear is held by the second coast
brake, the planetary gears walk around the sun clockwise and drive the
front planetary ring gear clockwise through the input shaft and torque
converter to the crankshaft for engine braking. In contrast, while in
second gear with the selector in D−position, the sun gear is held in the
counterclockwise direction only and the sun gear rotates in a clockwise
direction and there is no engine braking.

The advantage that 2−range has over D2" is that the engine can be
used to slow the vehicle on deceleration, and this feature can be used to
aid in diagnosis. For example, a transmission which does not have
second gear in D−position but does have second gear while manually
shifting can be narrowed to the second brake (B2) or No. 1 one−way
clutch (F1). These components and related hydraulic circuits become
the primary focus in our diagnosis.