Engine + Tranny Question

i got a new tranny and new engine...and the engine is on the hoist, i tried putting the tranny(w/bell) on the engine while it is on the hoist and it wont go all the way in...it seems somthing it stopping it, because i know the pilot bearing is the right size....are there any special ways of doing this?? or whats the problem...should i just keep trying to put it in? thanks
 
I have no idea if my experiences apply to trans and motor out of the car, but Ill put in my 2 cents anyways :)
Maybe the input shaft is too long, or the clutch is not lined up well with the pressure plate, the splines of the input shaft are not lining up with the clutch plate, or there is excessive pressure between the pressure plate and flywheel. Try spinning the output shaft with a old yoke, or even your fingers as you push in the tranny. Not sure if you can do this with the engine out, but pull the clutch fork forward somehow to relieve pressure as you wiggle the tranny into place. As it comes to the last few fractions of an inch, you can try tightening the housing bolts to pull it in all the way(not sure how safe this last one is, but it worked for me as I was on my back under the car...)