bevans0331

(2014 xlt 5.0) ok so i had brought my truck in a couple weeks ago to get them to take care of a hard shift from 1st to 2nd, so they serviced the valve body. The problem was taken care of and with everything fine i notice a very distinct clunk from 3rd to 4th. it only does it when cold and its a one and done kinda deal until the next cold start. If i were to let off of the gas right before the shift it seems to be worse. when i brought it back they could not get it to do it at all. All i have ever owned was ford and it can be embarrassing when the chevy guys are in the truck, any ideas? thanks.