trans leaking again after rebuild

once again my 727 is leaking from inspection cover, a slow drip as compared to the pouring out.hoping its just front seal, one strange thing since install has been a weird short whistling noise(very short duration) just when i get on it hard, cant figure that one out. trans was rebuilt at supposedly reputable shop,with my math skills it was fully rebuilt in under 4 hrs, does this sound about right?