. >> reporter: 4-year-old greyson and his mom chrissy can hear the rumble they know he is on the way. is jumping up and down and flapping his hands and just feeling so much joy. >> reporter: frank diaz looks forward to this stop all week. >> i see joy. i see when he jumps up and down he is excited. >> reporter: like so many little boys, greyson loves the roar of the garbage truck. >> hey, little buddy. >> reporter: few know greyson struggles with autism making it difficult to communicate. >> i didn't have a typical child who spoke or said mommy, i want to get out of bed. or mommy, "i love you." >> reporter: a few weeks ago when frank pulled up greyson broke his silence. >> he said "i want truck." it was a breakthrough into my world. and not only did he talk to me. he said three words. >> reporter: for a family living with autism it was a milestone. >> it is such a -- a rare but special moment between the two of us. honestly it was magical. >> reporter: the kellys have two boys. little brother parker who is just 2, shows signs of autism, but is too young to be officially diagnosed. >>