The 3 speed overdrive has a couple of gizmos sticking out of the tail housing. One is a solenoid and it looks like an electric motor. The other is the governor.

There are pictures of it on the pages in this list.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.