Performance TH350 &Turbo 350 Transmissions

A properly built TH350 can handle significantly more power than a stock transmission, but horsepower capacity depends on the internal components, vehicle weight, engine torque, gearing, tire setup, and how the vehicle is used. Twisted Torque™ offers TH350 transmissions in multiple build levels, from Twisted Street™ for street-driven performance vehicles through Twisted Pro™, Twisted Punisher™, and Twisted Executioner™ for increasingly higher-horsepower and more demanding applications. Choosing the correct build for your combination is more important than simply looking at horsepower alone.

Yes. A standard automatic-valve-body TH350 uses a vacuum modulator that should be connected to a full manifold vacuum source. The vacuum signal helps control part-throttle shift timing and transmission behavior based on engine load. Engines with aggressive camshafts or low manifold vacuum can affect how the transmission shifts, so the engine combination should be considered when setting up a performance TH350.

The TH350 uses a detent, or kickdown, cable to command a downshift when additional acceleration is needed. Unlike the TV cable on a 700R4 or 200-4R, the TH350 kickdown cable does not control the transmission's main line pressure. The transmission can operate without the kickdown function, but you will lose normal automatic passing-gear operation.

The correct torque converter should be matched to the entire vehicle combination—not just the transmission. Important factors include engine size, horsepower and torque, camshaft, vehicle weight, rear gear ratio, tire size, and intended use. A mild street car may work best with a lower-stall converter, while a more aggressive engine or drag-racing combination may require a higher stall speed. Twisted Torque™ can help match the converter to the TH350 and the vehicle rather than choosing a stall speed based on horsepower alone.

TH350 shift problems can have several causes. Incorrect or insufficient manifold vacuum, vacuum-modulator problems, governor calibration, incorrect fluid level, linkage issues, or internal transmission problems can all affect shift timing and operation. An adjustable vacuum modulator can be used to fine-tune part-throttle shift characteristics, but it should not be used to mask an underlying mechanical problem. If a TH350 suddenly changes how it shifts, the cause should be diagnosed before making adjustments.