Accord 91 Auto Transmission Problem

Hello Ppl i have an accord 91 auto transmission the enigine is F20A . My gear box broke down a few days back the torque converter was screwed so i got a second hand gear box of the same kind. Now the gear shifting is better and its changes the gear very smoothly while accellerating but when i am reducing the speed the down shifts are ok but when its shifts from 2nd to 1st it very jerky and when crusin on really low rpm n low speeds lik 5 to 10 i hear a noise and its feels kind of sheddering n something is vibrating. Please Help i have changed the whole gear box but still having problem with the smoothness especially that vibration on low speeds n rms and that noise. HELP ME

an over filled tranny? i over filled mine and now it shakes in second gear, mine an auto.