Transmission Problems(No reverse)

hey,can anyone help me ........my transsmision shifts in drive ,everything ok,but when shifting in reverse is not moving ,not an inch.So I take the transmission oil pan off ..........then the oil filter.....then the lower transmision ansembly............where i find 4 little motors(pumps) with wire going out of the transmission..........well I figure one is not working ,can this be the problem with the reverse and so can i order those 4 motors(pumps) and where can i find them to buy it
what's the part number ???where can I look .........

Thank's