I guess i should have come here prior to swap and feel quite a fool. Begging forgiveness and advice from those more knowledgeable. Recently my girl got burned on an 00 civic ex with 275k dude sold it to her full of stopleak and it made it 8 miles down the road and blew the headgasket. It has D16Y5 motor and auto trans. So i bailed her out of it being that i had recently acquired a '96 civic ex auto w/161k D16Y8 on it. It had major front end damage and reportedly rough shifting 2nd to 3rd but it started and ran prior to pulling motor for swap i had bought it for $200 for misc parts i needed for my 00 dx. Anyways a buddy of mine who has done a few honda swaps agreed to help me make this 00 ex a runner and its body and interior were in great shape so on last tuesday we got at it and pulled both motors and trans from their shells. Long story short we decided to try and keep the 00 DI6Y5 auto Trans in its original not knowing if all was compatible but noting that the blocks seemed identical. The D16Y8 engine bolted right up popped in with no problem. We started her up without changing the ECU and she ran ok but had a CEL and a D4 flashing. Still low on fluid so we added a few quarts of plain atf and popped into drive loudly and i moved her to another spot in the driveway maybe 25 ft. Turned her off and added more atf when i started her back up it SLAMMED into drive with a grinding noise and wouldn't engage and the speedo said we were moving. Oh **** i said "something is definitely not right here" Any help would be much appreciated. I am currently stumped on what our next step should be but we are presently pulling out the failed Y5 tranny and considering gambling on the rough shifting Y8. All other options or combos that will get a good reliable car out of this,i am open to,just not sure what they are.. Ideas?