[W126 Coupe] SEC engine/transmission question

[Josh Allen]

For those of you who have some experience disassembling your cars, I 
have a question.

How do you get the torque converter to seat correctly, and the 
transmission to bolt back onto the engine?

After pulling the destroyed engine out of my car, and separating the 
engine and transmission, I can not get the transmission to bolt back up 
with the "new" engine.

I've measured the depth of the flex plate, thinking that there might be 
a difference between the two engines (same depth on both, measured at 
multiple points), measured how far the torque converter is set down into 
the bell housing on both of the transmissions that I have access to 
(also the same depth).

When I try to bolt the transmission onto the engine, it ends up binding 
and bowing the flex plate.  If I pull it much further than the start of 
that, it binds up enough that the engine and transmission cannot be rotated.


On a related note, should the transmission input shaft be relatively 
free turning?  The old crusty tranny that came with my usable engine 
spins freely, while the input shaft on the one that I pulled out of the 
car won't turn at all, unless you spin the output shaft.


Thanks for any input, I had to call it quits for the night, after 
multiple attempts to get things to seat correctly, or to figure out if 
there was some difference between the two years of engines.

-Josh