4L60E 8AN Braided Transmission Cooler Line Kit, 15 ft

A complete 8AN cooler line kit for GM 4L60E and 4L65E transmissions: 15 feet of braided hose, two straight and two 90-degree 8AN hose ends, a pair of 1/4 in NPSM to -8 fittings for the transmission case ports, a pair of 1/4 in NPT to -8 fittings for the radiator tank, sealing rings, metal gaskets, hose separator clamps and thread tape. That is enough hose to run both the feed and return lines from the case to the radiator or to an auxiliary cooler.

8AN is a step up in bore from the 6AN kits most people run. It moves more fluid with less restriction, which matters when you add a big stacked-plate cooler, run a high-stall converter or tow hard with a built unit and want the cooler circuit to actually carry heat away. The hose has a CPE rubber inner core with a layer of 304 stainless wire for reinforcement under a nylon outer braid, and the hose ends and adapters are machined aluminum.

This is also the fix when the factory steel lines have rusted through at the frame clips, the crimped rubber sections are weeping at the ferrules, or a swap left you with lines that no longer line up. Drain what you can, remove the old lines, thread the NPSM adapters into the 4L60E case ports and the NPT adapters into the radiator tank with a wrap of tape on the NPT threads only (the NPSM ports seal on the O-ring and gasket, not the threads), then measure, cut and assemble the hose ends. Route the lines clear of the exhaust and anything that moves, secure them with the separator clamps, top off the fluid and check every joint for leaks with the engine running and the fluid hot.