Chevyboybigred

I have a 91 Chevy with a 700r4 I just put a motor in I was sitting at a light and went to go and it started to then nothing didn't make any strange sounds nothing drove fine shifted fine up till then I hauled truck home checked fluids n they were fine I jacked up rear tires n put in drive n they started to spin but when I hit the gas they don't spin any faster it's acting like it's not getting fluid thru the pump any ideas??