Trans not sliding into engine all the way
 

I have done this procedure many times but never been stumped like this..
Engine is an 86 3.2, formerly installed in a 76 with its original trans. The 76 trans has grown notchy and difficult to shift. So, I have a rebuilt 79 trans that I am installing. It slides into the engine ok, but stops short about a half inch. The spline lineup tool slides in and out fine. The pilot bearing shaft, spline, and guide tube are all the same diameter. The shift fork is in the pilot bearing groove. I have notched the housing for the sensors. What am I missing, or what have I done wrong? Thanks in advance for your help>

Put two bolts in each stub axel , set one side so it can't rotate, using a screwdriver.
Then rotate the other with another screwdriver and the input shaft will spin, allowing the splines to rotate to alignment .
While doing this push the trans further to mate with the engine
Ian

have you tried turning the engine over a little? This has happened to me more than once and a partial turnover using a ratchet on the crank pulley or fan bolt enabled it to slide all the way in.

Sometimes an edge of the engine sheet metal interferes been there a few times.

More detail-engine is on a lift cart, trans is on a trans jack with a tilting table.

Have you removed the clutch release arm from the release fork shaft? It can hit the heat exchanger if it's not removed.

Checked the pilot bearing to make sure there's not some FOD in there?

Clutch fork centered in the throw out bearing?

Half inch sounds like a pilot bearing thing--everything else would be lined up by that point.

Pictures please

^^ That's my first thought too.

If the trans is in gear you can rotate it to see in the spines are aligned. (But at 1/2' they should be engaged.) If it wasn't a Porsche I'd think of an alignment pin.

Any chance that something was left on a mounting stud?

Only last thing I could think of is moving the release fork to be sure it moves freely to show it isn't pressing hard against something.

The starter gear not retracted and banging into the ring gear?

Well duh!!! Now I will have to sit in the front row and pay attention again!
I removed the clutch pressure plate and flywheel in stages, and kept test fitting at each stage-no joy. Even down to a bare crankshaft, it still wouldn't go in. So then I noticed the other sensor at the top of the engine case, where I had overlooked it and not provided a cut out in the bell housing. So-a couple of minutes with the grinder and good to go. At least there was some benefit from all that trouble-I replaced a leaking rear main seal.
Thanks for all the answers.

Well you got it done. Good for you!
For future refer in case any else has this problem I thought I would mention that the sensor at the top is just a test sensor that no one ever uses. It goes to the little rubber plug under the idle control valve. It can be removed and discarded.