Transmission knocks and catches in forward auto

Check the fluid level and quality in the transmission. Its dipstick is on the left (from sitting inside the car, US driver's side) often hidden by hoses/cables. It is the only fluid that must be check while IDLING. If the fluid is low and coffee colored, time for a drain/fill or maybe 3 drain/fill cycles. Only about half the fluid will drain out. 3 cycles of drain, fill, drive-a-little with fresh fluid can often clean some deposits out of the trans. You can also try , on the last fill, to put in a bottle of Trans-X additive. It has helped a lot of people with 'delayed engagement' problems. The low-high marks on the dipstick are only about a pint apart - not a quart like engine oil so, refill a tiny amount when close to full. Without driving the car, difficult to suggest anything else. You might post the issue at w w w.subaruoutback.o r g for more help.