Overflow Tank- Trans Fluid GM 4L80E/4L85E

The Overflow Tank for Transmission Fluid GM 4L80E/4L85E by ATI Performance is an essential upgrade for serious transmission builders and high-performance enthusiasts running these legendary heavy-duty automatic gearboxes. When you're pushing a 4L80E or 4L85E transmission beyond stock parameters—whether in a drag vehicle, towing application, or heavily modified street engine—fluid expansion and thermal cycling demand proper expansion capacity that factory cooling systems weren't engineered to handle. This dedicated overflow tank prevents costly fluid loss, maintains consistent fluid level, and protects against cavitation that can damage internal clutch and pump components.

ATI Performance's overflow tank is engineered with precision dimensions (3.9 x 2.85 x 12.7 inches) to integrate seamlessly into tight engine bays while providing adequate volume for fluid displacement during sustained high-temperature operation. The compact, lightweight design at 1.48 lbs minimizes parasitic weight while the purposeful tank geometry promotes smooth fluid return and prevents air entrapment in the transmission cooler circuit. The tank features proper inlet and outlet porting designed specifically for the 4L80E and 4L85E transmission lines, ensuring pressure-balanced operation without backpressure issues that could starve the torque converter or restrict cooler flow.

This overflow tank is ideal for builders preparing vehicles for competition, aggressive street application, or maximum-effort engine conversions where the 4L80E/4L85E is the transmission of choice. Installation pairs perfectly with an aftermarket transmission cooler upgrade and complements larger displacement engines, turbocharged builds, and high-stall-speed converters that generate elevated fluid temps. The tank integrates with stock or aftermarket cooling lines and works in conjunction with proper fluid maintenance protocols to extend transmission life under demanding conditions.