Overflow Tank - Trans Fluid - GM TH400

The ATI Performance Overflow Tank for Trans Fluid is a compact 1-liter auxiliary transmission fluid reservoir designed specifically for the GM TH400 transmission. This aluminum tank with black powder-coat finish mounts directly into a custom transmission cooling system, capturing overflow fluid during thermal expansion and preventing loss of hydraulic pressure critical to TH400 performance and longevity.

The tank features a 1/8-inch NPT male inlet connection that integrates seamlessly into your transmission's cooling circuit. At 1.4 pounds and measuring 4.15 x 2.8 x 12.9 inches, it fits tight engine compartments common in modified vehicles where space is limited. The powder-coated aluminum construction resists corrosion from thermal cycling and protects against fluid degradation from external contamination. One-liter capacity is sized to handle normal thermal expansion without requiring constant topping-off, yet remains compact enough not to interfere with other underhood components in most installations.

This overflow tank is essential for TH400 transmissions in high-performance applications—drag racing, street rods, high-horsepower trucks, and serious off-road builds where sustained heat generation pushes transmission fluid beyond factory cooling capacity. When transmission fluid temperature rises, pressure increases; without overflow provision, seals rupture and fluid escapes. The ATI tank captures that overflow, allowing it to cool before returning to the main system, stabilizing operating temperature and extending transmission life under demanding conditions.

Serious TH400 builds benefit from aftermarket cooling solutions because factory radiators and coolers were designed for stock duty cycles. Adding transmission fluid capacity and overflow management is standard practice among transmission shops and performance builders who understand that heat is the enemy of transmission longevity and shift quality.