Automatic Transmission Cooler Flow

Often times it is necessary to know which, of the two hydraulic cooler fittings commonly found on a particular automatic transmission, is the "pressure" side, and which is the "return side". Obviously, the transmission fluid will flow from the "pressure" fitting, through the transmission cooler, and, on to the "return" fitting. Knowing which direction the fluid flows through the cooler can be helpful when installing an auxiliary cooler, installing a check valve (to help eliminate fluid drain-back from the torque converter), or to "flush" the transmission (when the fluid becomes severely oxidized, it may be desireable to drain the fluid, and then utilize cooler flow to pump more old fluid out, while filling the transmission, with the engine running). To help figure out which direction the fluid may be flowing, refer to the following table for many of the more popular transmissions.

General Motors

Transmission		Cooler Pressure Fitting (on transmission)
125/125C (3T40)		Bottom
180		Bottom
200/200-4R		Top
325/325-4L		Bottom
350		Bottom
400/4L80e		Bottom
440-T4 (4T60)		Bottom
700-R4 (4L60)		Bottom

Ford

Transmission		Cooler Pressure Fitting (on transmission)
A4LD		Bottom
AOD/FIOD		Top
ATX		Bell housing end
AXOD		Top
C3, C4, C5, C6, E40D		Front

Chrysler

Transmission		Cooler Pressure Fitting (on transmission)
904/727		Front
500/518/618		Front
404/413/470/670		Bottom
604

Foreign

Transmission		Cooler Pressure Fitting (on transmission)
Honda		Over Bellhousing
Jatco (RWD)		Front
Mitsubishi		Inner
Renault		Top
Nissan RL3FO1A		Top
Nissan RL4FO2A		Front
Subaru		Top of differential
Toyota FWD		Top
Toyota RWD		Front