all my gears where slippin so i decited to change my trasmission, i never really did it passport tranny before, and now that i have everything put back together the engine isn't spinning ive tried using a pri bar spin the flywheel but its lock... i have a feeling i have to drop the trasmision again but i wanna see if it could be caused by anything else... anyhelp helps

 

sounds like the flexplate is backwards, if you removed it, but there is no reason for that, or possibly internal damage to the used trans.