"Take it back and have them check it."

"But when I put it back in, now the car won't shift?!? "

Dunno what good taking it back to himself would do:). Unless he meant "I" as in him taking it to a shop.:)

So the car will go into D? Or will it just spin like it's in N?

Do you mean it will take off in 1st but wont go to 2nd/3rd/4th? Or wont shift at all, period?

Did you take out the transmission to install the engine? Theres a sensor box i believe on the very front of hte A604, check to make sure everythings ok there. Theres also the shifter, dunno why that woulda been messed with but thats up there too. Does it have fluid in it? Wont shit without fluid. Umm...Was the torque converter put back in?;) jk lol Lots of things to check man be more specific about what its doing!:) Hit me up on aol at brohymn411 if you want, ill see what I can do by what ya tell me.

Joseph