retained from the older controlled coupling Hydramatic). The Roto was adopted for all Oldsmobiles as well as Pontiac's full-sized Catalina, Ventura, and Grand Prix models, while all Cadillacs and Pontiac's Bonneville and Star Chief models retained the older four-speed Controlled-Coupling Hydra-Matic unit. Controlled Coupling HydraMatic and Roto HydraMatic both have the "Split Torque feature" whereby, in high gear, the torque is divided 40% through the fluid coupling and 60% through mechanical connection, which made these transmissions more efficient than any other automatics before the lock-up torque converter was used. Hydramatic transmissions were ultimately replaced by a new three-speed torque converter automatic transmission called Turbo-Hydramatic in 1964 and 1965, whose design was more similar in principle to the Chrysler TorqueFlite and the '51 Borg-Warner-designed Ford Cruise-O-Matic than the fluid coupling Hydra-Matic the "Turbo" replaced. The original Hydra-Matic continued to be used in light trucks and other commercial vehicles until 1962. It was subsequently replaced in that role by Chevrolet Division's Powerglide (where it was dubbed "Pow-R-Flow") in the GMC light truck line, and later, in 1966, with the Turbo Hydra-Matic (THM) in GMC light trucks, whose simplified design was much less costly to manufacture. Chevrolet Division's light truck line used the less-than-adequate Powerglide all through the 1960s until Turbo-Hydramatic was made standard in 1969. Cast-iron Hydra-Matic production ceased at Willow Run after the 1962 model year, and Controlled-Coupling Hydramatic ceased in early 1964, allowing retooling time for the Turbo Hydra-Matic 400, which debuted in the 1964 Cadillac models in mid-year, with Pontiac Division's Star Chief and Bonneville models being the last to use the Controlled-Coupling Hydramatic (Model HM315) of any GM car. 1964 Turbo-Hydramatic production used a selector quadrant similar to Chevrolet's Powerglide in that there was only one "Drive" position and a "Low," although it was a true three-speed unit. This was improved upon for all 1965 models with the "D L2 L1" or "D S L" quadrant, which allowed "dual range" flexibility as did the Dual-Range Hydramatic of 1953-1955. It was this version that replaced all Roto Hydramatic and Controlled-Coupling Hydramatic models in GM cars in that year, ending twenty-four years of four-speed automatic transmission production that obviated the need for a torque converter. Despite the name, the Turbo-Hydramatic has no mechanical or design related to the original Hydra-Matic, or the Controlled-Coupling Hydramatic. Hydra-Matic was a complex design that was expensive to produce. Despite some early problems, it was