The Twin Turbine was basically a single speed transmission with a low multiplier. It did have a low gear if selected, and when the pedal was mashed to the floor the thing went into fine pitch and took off, then shifted into high range at 45-50, and then the torque converter really took off and it was a steady pull at about 2500 to 130 mph or thereabouts. If you left the car in "drive", all you heard was it revving up a bit and then holding at about 1900-2000 and then a steady suck-you-back-in-the-seat pull to top speed. Driving a Dynaflow (or Twin Turbine as they were known later) is an experience you'll never get in a modern car. They were a lot smoother than the powerglide, the powerglide worked on a different philosophy than the Dynaflow. How I discovered it was just fooling around with a half-dead old 60 Invicta that I had just roused from a 10 year slumber in a bush. I just did what I had to do to drive it. It wouldn't dynaflow properly, so I had to manually shift it. And of course, I was young and broke at the time, not to mention there was nobody around here who even knew what dynaflow was. Triple Turbine was a forerunner of the Turbo Hydramatic series. They added a grade retarder and tried to tighten the whole works up. No it didn't work very well and was only offered in 58 and 59. By 60 it was no more. So by 1963 GM decided to marry the "Slim Jim" Jetaway Hydramatic (which was a dog) Chevy Powerglide and Buick's torque converter expertise, and came up with the Turbo-hydramatic series.