Meet the sensation of the American automotive scene for 1966, the Oldsmobile Toronado, and its revolutionary drivetrain system known as the Unitized Power Package.
The effort that ultimately produced the 1966 Oldsmobile Toronado began back in 1955 with a General Motors Motorama show car, the LaSalle II. While its experimental front-wheel drive system wasn’t ready for showtime and never went public, the development work continued and by 1958, GM had settled on a modular configuration called the UPP, or Unitized Power Package. Its objective was to fit a V8 engine, automatic transmission, and final drive into roughly the same space normally occupied by the engine alone.
When, some years later, the 1966 Toronado was introduced on October 15, 1965, it was the sensation of the American automotive scene. While Cord and Ruxton had pioneered front-wheel drive in the USA back in the 1930s, not much had happened on that front since, especially in the Motor City, and the Toronado was heralded as revolutionary. The car was showered with numerous industry awards and nearly every automotive and workbench magazine ran detailed stories on the car and its unusual driveline setup.
The schematic drawing above provides an overhead view of the basic layout. The engine was placed in the conventional North/South location, but offset a few inches to the right. Meanwhile, the transmission was essentially split in half, with the torque converter remaining at the rear of the engine and the rest of the unit rotated 180 degrees to face forward.
This modified version of the Turbo-Hydramatic 400 was known as the THM 425, and the differential bolted directly to its case, tucked under the left bank of the 425 cubic-inch V8. Since an offset pinion was neither required nor desired, the ring-and-pinion set was spiral-bevel rather than hypoid. Rzeppa-type constant-velocity universal joints provided the steering and suspension articulation for the paired driveshafts. GM reported that the system underwent 1.5 million miles of testing in more than a dozen road mules.
One major challenge was the transfer drive between the torque converter and the transmission’s input shaft. After various gear-drive systems were tried and found lacking, the engineers settled on a two-inch wide Morse Hy-Vo silent chain two inches wide and a pair of 7.5-inch sprockets. Developed in partnership with the Morse Chain division of Borg-Warner, the steel link-belt chain proved to be quiet and reliable. Unlike the earlier Cord and Ruxton, the Toronado and its UPP never developed a reputation for trouble among the car-buying public.
One year later, Cadillac adopted the UPP for its front-drive luxury coupe, the Eldorado, with a Cadillac V8 substituted for the Olds powerplant. The UPP/Olds V8 combination then got its most rigorous test in the 1973-78 GMC Motorhome (below) and filled the bill. In 1979, the UPP was reengineered for use in the downsized Toronado, Eldorado, and Buick Riviera, with a smaller and lighter THM 325 transmission replacing the THM 425. This system remained in production through 1985 when it was replaced with a transverse-fwd package, by then the industry standard.
