#thm400

We return to the Turbo-Hydramatic once more today, and our third installment sees us at a critical point in the timeline of the automatic transmission. Fuel economy pressure from the government and performance demands of the consumer increased considerably in the intervening years since the THM’s debut in 1964. That meant the creation of lighter, more compact, and cheaper versions of the Turbo-Hydramatic compared to its flagship shifter, the THM400. GM branched out into the likes of the THM350, THM250, and the very problematic THM200.

In 1987, GM stepped away from the traditional THM naming scheme and switched to a new combination of letters and numbers. Number of gears, layout, and strength combined to turn the THM400 into the 3L80. But the hefty gearbox was already limited by then to heavier truck applications; passenger cars moved on to four forward gears after the dawn of the Eighties.

Our Abandoned History coverage of the Turbo-Hydramatic transmission series continues today. The THM was a singular solution to two different automatic transmissions in use by Oldsmobile, Cadillac, and Buick in 1963. Turbo-Hydramatic arrived at a time of modernization for the automatic, which prior to the mid-Sixties was regarded as inefficient and less than smooth.

The THM400 was the 1964 replacement for the Hydra-Matic and Buick’s Dynaflow and established itself as a smooth and reliable gearbox. It proved useful in a variety of luxury and heavy-duty applications and shrugged off weight and torque easily. In short order, it took off as the transmission of choice for various small manufacturers outside of GM. However, no matter how excellent the THM400 was, it found itself squeezed by a drive toward greater fuel efficiency. It was also a bit hefty to be of broad use in smaller or lighter passenger cars. GM needed more Turbo-Hydramatics!

In Part I of our Abandoned History coverage of GM’s Turbo-Hydramatic transmission line, your author made reference to a very exclusive Nissan that made use of the hefty THM400. That extremely formal Rare Ride has been on my mind since then, so here we are. If it pleases your majesty: The 1966 Nissan Prince Royal.

A few weeks ago, we concluded Abandoned History’s two-part coverage of the Chrysler UltraDrive transmission. Within the comments was a request for more transmission coverage of an equally abandoned nature. Let it be so! Come along as we discuss the vast automatically shifted expanse that was the Turbo-Hydramatic transmission family, by General Motors.