Automatic gearbox - Jatco (Power Flows): Description and operation (page 4 of 6)

4th Gear (D selected)

1 High clutch 2 2-4 brake 3 Front planetary gear 4 Rear planetary gear 5 Low one-way clutch 6 Input shaft

7 Output shaft 8 Idler gear 9 Reduction planetary gear 10 Reduction brake 11 Reduction one-way clutch

On 4th gear selection, the high clutch, 2-4 brake, and the reduction brake are engaged. During acceleration in 4th gear, the reduction one-way clutch is locked. Power flows from the input shaft to the front planetary carrier to rotate clockwise by the high clutch. The 2-4 brake locks the front sun gear. The front pinion gear rotates clockwise and forces the front planetary carrier to rotate clockwise simultaneously. This allows the front internal gear to rotate clockwise and transmit power to the reduction internal gear via the output gear and idler gear. The rotational speed of the planetary carrier is faster than 3rd gear because of the rotation of the internal gear. Power is then transmitted to the road wheels in the same way as 1st gear.