Had Transmission Rebuilt now i'm

getting a squeaking or chirping sound coming from near the bell housing. it's been 2 months since rebuiuld but i noticed it about a week after and thought it was a water pump or something. i used a stethoscope on all the parts with pulleys etc until i realized was coming from near firewall. the sound goes away after the engine is hot. read some posts about flexplate problems so i called the shop that rebuilt the tranny and they said since the sound goes away its not the flexplate. i'm pretty sure this is related to the rebuilt trans some way. btw it 96 Explorer 4.0 4wd AT. tia.