I have an 02 Sunfire 2.2 with auto trans. I recently replaced tranny with 54000 mile junkyard tranny. When i initially start the car and put into either R or D it shifts in smoothly and pulls out. As i begin to drive, the car will not shift from second and has no power, just builds RPMs. After a stretch(1-3 miles typically), it feels as though it shifts hard into gear and operates fine. Tranny shifts up and down smoothly, come to complete stop and goes through all gears perfectly. However after it begins shifting fine, absolutely no slipping or anything, but if i put tranny in N and then go to D or R it drops in quite hard unlike when its not shifting through gears. Also if i turn ignition off and start car right back up, im back to not shifting properly at first. It seems to begin shifting quicker than starting from cold though. I have driven it 20 miles after it began shifting fine with no issues but turn it off and back on and theres a period of malfunction. Im pretty lost and way beyond frustrated at this point. Im thinking MAYBE tranny control module but appreciate any input i can get. Thanks in advance!!