4L60E 6AN Braided Transmission Cooler Line Kit, 20 ft

The factory steel cooler lines on 4L60E trucks and SUVs rust through at the clips and crimped fittings, and a pinhole there dumps ATF fast. This kit lets you build a new pair of lines from scratch in 6AN braided hose instead of chasing an OE line that no longer comes in the right bend. Twenty feet of hose is enough to run supply and return from the case to the radiator tank, or out to an auxiliary cooler, with length left over.

The kit includes 2 straight and 2 90-degree 6AN swivel hose ends, 2 6AN to 1/4 in NPT adapters, 2 6AN male flare to 9/16-18 inverted-flare (1/4 in NPSM) adapters, 2 hose separator clamps and a tube expander for seating the hose. The NPT adapters thread into an aftermarket cooler or case port; the 9/16-18 flare adapters are the common GM cooler fitting size. Check your radiator tank port thread before you start, since some tanks use a different fitting.

On the bench: cut the hose square with a cutoff wheel, tape the braid first so it does not fray, push the hose into the socket, then thread the nipple in and snug it without bottoming it out. Route the lines away from the exhaust and use the separator clamps to keep supply and return from chafing each other. Pressure-check at idle in gear and look for weeps at every fitting before the truck leaves.

The hose is a CPE rubber liner with a 304 stainless reinforcement layer and a nylon outer braid, rated 750 PSI working and 2250 PSI burst from -22 F to 248 F. It also works on 4L65E and other applications that take 6AN line.