R Position

While in R position also, the valve operates by the balance of reduction brake operation pressure (38) and back pressure of accumulator control valve B (39), the same as when in the forward drive ranges. However, while in the R position, since the line pressure (reverse clutch operation pressure) is applied to the oil passage (4), the line pressure is applied to the reduction brake irrelevant of the valve motion.

Fig 1: Identifying Reduction Reducing Valve Operation
Courtesy of MAZDA MOTORS CORP.