How do you get the torque converter fully seated?

There are two things to consider when seationg it. You have slits on the converter hub. The mtach up with the pump splines, should be two of them, and you simply sping it until they seat. Then the next issue is getting the the splines on the input shaft to match so you can slide it the reast of the way and get it past the seal as well. Make sure, before you start putting it on at all, that you can rotate the input shaft a little bit. If not, you might have to put the tranny into neutral. Also put some grease on the lips of the seal that is in the tranny that seals the converter hub. Keep the coverter square, straight in line with the input shaft, when you are putting it on. Before you put it on, you might be able to look into the tranny and see the two pump splines since they are pretty big and line them up as much as possible so you don't have to rotate it much. Once they meet up and kind of start meching into each other gently puch and turn the converter left and right just slightly to get the input shaft splines to line up so you can slide the conveter the rest of the way on. This may be hard to do if the tranny does not have much of an inspection cover area so you will have to turn the tranny left and right to get it on the shaft. The biggest thing that makes it hard is keeping it sqaure, in line with the input shaft. Use the face of the tranny compared to the engine block where it mounts to keep it square at all times or it won't go on. It just takes some time. I have struggled with manual and auto trannsmissions in and out of cars and it is never easy and it can take some puching to get it to slide all the way on. But by no means force it, beat on it or anything like that.

I am stumped as well. Did you check to see if there is at least some rotational play in the input shaft so it could line up with the splines? Of course if you are rotating the converter slightly it should not matter. Since you have it so far I don't think that keeping it sqaure or the converter face flat so the hub is not cocked at all and can get past the seal, you should be past the seal. There may be a sleeve that it has to slip into to drive the pump. I really do not know what could be going on.
This is the converter that came off of this transmission correct?
That is really an odd one. Have you tried turning the converter 180 degrees or some other large rotation to see if it makes a difference?
If you still have trouble, let me know and I will ask another tech friend of mine if he has an idea. It may take him a bit to respond as he is very busy though. I am sorry I cannot think of any reason it would hold up like that.

I sent a message to a friend of my whos handle is, "saturntech". He is really good and if he has time, he will help you out.
Let me know if he has not gotten back to you by tommorrow afternoon and I will send a message to another friend. Hopefully, and they probably will unless they are out or swamped, they will respond soon and we can get some idea to helpo you out. It is really odd, but one of these guys might just know a trick as they have seen it all. It will just be a matter of time and them being able to get back to you if they are able. They will not leave you hanging. They always help as we help each other, so if saturntech does not get with you tommorrow, he is either not working right now or just can't take any more workload. The smae will be true of my other friend. I am sorry I have not been able to figure out a solution but I have never n=been so stumped. Both of these techs have helped me out and I have helped them when it comes to expertise, but this is a tough one. But maybe not to one of them.
I hope we can get you figured out. We have not failed at solving a customers problem yet, so just hang in there. I know this is frustrating as I have fought with a few trannys myself and this kind of stuff happens. I usually just had issues with getting it to line up perfectly as it is a tight and has to be perfectly straight to get a converter or even a manual tranny and clucth to seat correctly. Don't get frustrated and start threading nolts and tightening bolts to pull it the rest of the way, it could damage something.
So, I will look tommorrow afternoon, I will probably be working anyway, and get with you to see what the status is.
Take a break and get away from the car and relax for a while. Sometimes that can help a lot more than you think it would.

What works for me is slide the torque convertor in then put pressure on it. But dont dont spin it in a circle while pushing on it. While pushing on it turn the torque about 60-90 degrees left to right it should slide in. Then you will hear a light scraping noise from the torque convertor lightly scraping on the torque convertor housing when its in all the way.

So let me ask you this why did you remove the transmissiin and torque convertor from the transmission?

Glad to hear it sounds like the other one you couldnt get in was just not the right one or damaged some how. Let me guess the other one slid right in?Your welcome thats what were here for.

You have a great night also.