How to Identify a Turbo 350C

by Dakota Wright
old car image by John Sfondilias from

Hot rod enthusiasts can attest to the popularity of the Turbo 350 transmission. The TH350 (Turbo Hydromatic 350) was a transmission developed in a joint venture between Buick and Chevrolet in the late 1960s. This transmission was designed for small block 350 engines manufactured by Chevrolet.

The Turbo 350 underwent few changes in the seventeen years it was manufactured. The most noticeable change, made during the early 1980s, is the addition of an electronically controlled lock-up torque converter. The addition of this technology improved highway driving speeds and made the transmission more efficient. This modification in the Turbo 350 transmission design is known as a Turbo 350C.

Step 1

Drive the car onto the car ramps carefully. Turn off the engine and place the car in park. Set the emergency brake as a precaution. Place the wheel blocks behind and under the rear wheels. Hydraulic floor jacks and jack stands can be used in place of car ramps.

Step 2

Turn on the drop light and position it through the engine compartment. The safest place to put a drop light is between the firewall and wheel well. The goal is to illuminate the area near the flywheel and torque converter on a Turbo 350C transmission.

Step 3

Position the mechanic's creeper in front of the driver's side of the vehicle between the front wheels. Sit down and carefully slide backward until you reach the side of the transmission facing the driver door. This is the side opposite the transmission coolant lines.

Locate the bell housing on the 350C Turbo transmission. Directly behind the bell housing, on the driver's side, is the passing gear linkage. Next to the bracket that holds the linkage is a four-pronged electronic plug. This electronic plug is unique to the Turbo 350C transmission and is the only way to accurately identify this transmission from other 350 models.


  • The Turbo 350C was manufactured between 1980 through 1986. If the car is "stock" (original) and has a 350 small block or V6 equivalent, chances are good that it came with a Turbo 350C. Do not be fooled by the shape of the transmission fluid pan. The fluid pan is typically changed to improve performance.
  • If the Turbo 350C transmission is not in a vehicle, you can identify it by examining the input shaft. Turbo 350Cs have a hollow input shaft where the torque converter slips on. An "O" ring will be in a grove 1/4 of an inch back from the front of the shaft. Earlier model Turbo 350 transmissions had a solid input shaft.
  • A Turbo 350 transmission can come with three different bolt patterns. The bolt pattern is not indicative of the transmission's originality.


  • Disconnect the battery to ensure the vehicle cannot be started.
  • Place the wheel blocks per the manufacturer's instructions.

Items you will need

  • Car ramps
  • Wheel blocks
  • Drop light
  • Mechanic's creeper
  • Flash light

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