Comprehensive guide to the GM TH400 automatic transmission — specifications, identification, history, and adaptability for Jeep conversions.

These transmissions mate a three-element turbine torque converter to a Simpson planetary geartrain, providing three forward speeds plus reverse. The Turbo-Hydramatic or Turbo Hydra-Matic (THM) …

The TH400 is an aluminum cased three speed automatic transmission that was produced by GM. It was introduced for the 1965 model year and made its debut in Cadillacs, and is respected for its durability …

ATI now has an answer for this market and offers three variations of a 2-speed Turbo 400! OEM cased units are rated to 1800 HP and not intended for heavy weight cars. ATI SuperCase recommended …

Sep 11, 2025 · The TH350 and TH400 are GM’s most legendary transmissions. Learn the differences in strength, weight, performance, and applications.

The TH400 was launched by General Motors in 1964, as a replacement to the ST300 2-speed automatic transmission. It was used in a wide range of vehicles, hence, it was not just exclusive to GM cars.

The TH400 is a venerable transmission that has its roots in mid-century automotive tradition but has since been modified for modern use. It is an automatic shift, positioned longitudinally behind the …

Jan 9, 2026 · Discover how the TH400 transmission evolved from muscle cars to modern performance. Learn about key upgrades, durability, and why it's still a top choice today.

This chart breaks down the six types of Sonnax TH400 transmission parts available at different performance levels. Combine these with other Sonnax TH400 upgrades for a top-notch rebuild.

Aug 3, 2023 · Since many of us own at least one GM Squarebody truck with a TH400, I figured I'd start another all-encompassing thread, this time on the Turbo Hydra Matic 400 aka THM400...I have basic …