General Motors produced the TH350 or Turbo 350 three-speed automatic transmission to equip its Chevrolet, Buick and Pontiac cars beginning in 1969. GM usually paired the Turbo 350 with small-block Chevy engines, such as the 327 and 350 V-8s.
The Turbo 350 came encased in a one-piece aluminum alloy housing unit. It measured 21.75 inches long and weighed 120 lbs. GM installed a lock-up torque converter in 1979 through 1984 vehicles. An electrical plug on the driver’s side of the transmission identifies the lockup converter, according to Novak Conversions.
GM introduced the Turbo 350 to replace the venerable Powerglide two-speed automatics. The Turbo 350 featured gear ratios of 2.52-to-1 for first gear, 1.52-to-1 for second and 1.00-to-1 for third. In contrast, the Powerglide had gear ratios of either 1.82-to-1 for first and 1.00-to-1 for second or 1.76-to-1 for first and 1.00-to-1 for second.
The Turbo 350 automatic found its way into Chevrolet Camaros, Pontiac Firebirds and Chewy and GMC trucks. Although the transmission most notably matched GM vehicles with small-block V-8s, it also matched the block-block 396 V-8s, V-6s and the small Iron Duke in-line four-cylinder models. GM also manufactured derivatives of the Turbo 350 with the smaller TH20, TH250 and TH375, which include lock-up torque converter models.
