transmission is not spinning and engine won't turn over on 1995 Ford F-250

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I just installed my rebuilt 401d transmission. It started, appeared to be building pressure, started spinning...then it all stopped. Now my truck will not even turn over. Any ideals?
(1) Answer
what was building pressure? the trans? that happens the second you start it.
How much fluid did you put in before you started it? if it is an E4OD it hols about 15 in the pan and a total of 25 in the trans. if you put too little in it, you may have cause internal damage already.