I recently just got done my complete rebuild of not only my engine but also my trans. I have a 2004 impala ls and originally did a top swap on it along with an xp cam but had a problem with that engine and shattered a piston. I then bought a lower milage l32 engine and completely rebuilt from new diamond racing pistons to having the engine fully balanced and machined. I also got a northstar throttle body, new xp cam, zzp headers and 3.4 pulley. I sent out for a mail order tune from zzp for all the new mods. Then I had the trans completely rebuilt from a 2000 bonneville ssei case and upgraded to 3.29 gears, hd parts, Transgo shift kit, aluminum pan and zzp chrome moly pump shaft. When I went to fire it up the engine sounded healthy and filled the trans with oil and it took the oil and I had to out more in but when I took her out for her first test drive she didn't want to shift out of first. The car actually felt like she was in neutral whether in reverse or gear. I unplugged the harness from the trans and manually shifted her and she felt the same exact way. I ran a full diagnostic on the car and it came back perfect, nothing was wrong with the sensors or anything no codes were being thrown. I then pulled the pan off today and the filter was still attached and the trans fluid still look brand new. I used my old harness from the original top swapped l36 for the new l32 and adapted it for the new throttle body. I also used the original internal trans harness from the original trans that came with the impala and wired it all correctly. The pressure sensors were also the same as the original. Everything seems to be 100 percent right for what I know and have done and researched but I can't figure out why the trans is the way it is. Would u have any suggestions or ideas what it could possibly be?
