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The Turbo 350 transmission was introduced beginning in 1969.
This transmission was a 3 speed automatic transmission developed jointly by Chevrolet and Buick. Although they were both under the General Motors umbrella, at the time they acted as completely separate entities, whereas now the developers at General Motors powertrain work only for GM, not Chevrolet or Buick.
This transmission replaced the GM Powerglide automatic transmission, which was a 2 speed automatic transmission that was in production for 23 years.
The Turbo 350, known by the name TH350, was used in nearly all GM rear wheel drive car and truck applications during its tenure. To name a few, this transmission was used in the Caprice, Chevelle, Corvette, Blazer, and Nova.
The TH350 was introduced in 1969 as a replacement to the Powerglide 2 speed automatic transmission. While the phase-in began in 1969, it was not complete until the 1973 when the Powerglide fully phased out.
This transmission was in production for about 15 years, being fully replaced by the 700R4 in 1984. In addition, a TH350-C added the lockup torque converter capability and was introduced in 1979.
While the TH350 is no longer in production, the transmission is still used for many classic car builds. The TH350 was popular for a variety of reasons. The simple fact that this transmission had an extra gear compared to its predecessor is an advantage from the start.
This transmission is also known for being strong and versatile, in addition to being quite compact.
One of the weaknesses noted about this transmission was wobble of the direct clutch drum.
Turbo 350 Performance Specs
The maximum torque that this transmission could handle varied depending on the application to which it was being applied. The transmission would be modified so that the transmissions behind the stronger engines were able to handle the additional torque.
The most torque from an engine that this transmission was applied to was 410 lb-ft. This is an automatic transmission that is longitudinally mounted, making it applicable for rear-wheel drive cars.
This transmission is a 3 speed, and no overdrive gear was available. The gear ratios used for this transmission were 2.52 for 1st gear, 1.52 for 2nd gear, and 1.0 for 3rd gear.
Construction and Size
The Turbo 350 transmission was a single piece transmission with the bell housing integrated into the transmission body. The transmission casing is made of cast aluminum.
The TH350 was also known for its quite short length, with an overall length of 21.75”. That also converts into a lighter transmission that carries a weight of 120 pounds.
The TH350 takes about 4 quarts in the pan, and then requires additional based on the torque converter being used. When combined with a 9.5” converter, the overall requirement is around 10 quarts.
The Turbo 350 transmission, commonly known as the TH350, was a 3 speed automatic transmission that began phasing out the GM Powerglide in 1969. The TH350 then lasted 15 years before eventually being replaced by the 700R4.
The TH350 offered a substantial improvement to its predecessor, with the additional gear being an obvious improvement from the beginning. During its time of usage, the TH350 was used in virtually all rear wheel drive vehicles from General Motors, including the Corvette, Chevelle, and Nova. This transmission was very popular due to its strength and versatility, as is still used in many vintage cars to this day.