Reverse Gear

The input shaft drives the reverse idler gear.
The reverse gear on the input shaft drives reverse gear on the output shaft.
The reverse gear synchronizer is splined to the output shaft.
When the reverse gear synchronizer sleeve is shifted rearward, reverse gear is locked to the output shaft. The reverse idler gear drives reverse gear on the input shaft, in a reverse direction.
The output shaft drives the differential ring gear.
The power flows through the side and pinion gears to the half shafts.

Fig 1: Identifying Power Flow - Reverse Gear
Courtesy of FORD MOTOR CO.