Help with installing auto transmission

I need some help, I have been replacing my auto transmission on my 2006 chevy aveo LS with my brother, we were able to get the transmission out no problem getting the new one in has been some what of a problem. We had installed the converter on first then jacked the transmission up in and got it inside the spline. But it doesnt seem to fit just right, it doesnt seem to be mating just right we get it up close to the engine enough to get the bolts in but when we start to tighten them we cant get the trans and the engine to be flush it has a few mm of gap between them. Something is just not right, are we not in the actual spline inserts, thats the only thing i could think that it could be. Please if anyone could help it would really help me out, spent all day today trying this and that to get it.

spray some PB Blaster into the rear of the crankshaft and see if there is anything (slude, debris, etc) that is preventing the input shaft from the trans from mating correctly.

are you sure you have the torque convertor on correctly? and not resting on the alignment pins?

if you get it that close it the splines should be correct, i think you would be about an inch or more out if the splines were not inline.

Actually, it's much easier to put the converter into the transmission, and line up the converter studs to the flexplate.

Yes make sure the converter is ALL the way in the trans and engaging the pump drive, then position the trans into place. Installing the converter is done by feel, and this is hard to do if the trans is in your way.

On automatics your suppose to install the converter into the transmission before you put the transmission back on. If you dont do this you will damage both the transmission and converter. The converter is supposed to be pushed into the transmisison and turned, until it drops in and locks into place. This cannot be done if you install the converter to the flex plate and then try and install the transmission.