Two 70-inch PTFE-lined 6AN braided lines with NPT adapters and 90-degree fittings to replace cracked rubber cooler hoses on a 4L60E, 4L80E, TH350 or 700R4.
This kit is built for the person plumbing a GM 4L60E into a swap, a hot rod or a truck that needs new cooler lines from the case back to the radiator or an auxiliary cooler. You get two ready-made 70 in. 6AN lines with a PTFE inner liner, stainless braid and a black nylon outer cover, plus the adapters that usually send you back to the parts counter: four 6AN to 1/4 in. NPT, two 6AN to 3/8 in. NPT and four 90-degree 6AN male-to-male fittings. Because the lines arrive finished, there is no cutting braid or assembling hose ends on the floor.
A 4L60E does not just send hot oil to the cooler for temperature control. Fluid leaving the torque converter goes out through one line, through the cooler, and comes back through the other line to feed the lube circuit that keeps the bushings, planetary gears and clutch packs alive. Sonnax describes the pump, pressure regulator, converter, cooler and lube circuits as connected in series, so a problem in the cooler plumbing shows up inside the transmission. The PTFE liner in these lines does not swell or soften from hot ATF the way old rubber hose does, which keeps the inside diameter at a full 3/8 in. and keeps flow where it should be. A braided line also stands up to rubbing and road debris far better than a bare rubber section.
Check the fluid level hot, then wipe the lines and fittings clean, drive the vehicle and inspect again. A cooler leak usually shows up at a joint, not in the middle of a steel run. If the transmission already has a slipping 3-4 shift or burnt fluid, read our 4L60E common problems guide first. A history of low fluid often means the 3-4 clutches are damaged, and our S10 4L60E guide walks through the same failure pattern on the smaller trucks.
The listing names the GM 4L60E, 4L80E, TH350, TH400, 700R4 and 200-4R, plus the Ford AOD and 4R70W. It is not tied to a specific vehicle or year range, which is why it is a favorite for swaps. The key is the port thread at each end. The included adapters cover 1/4 in. NPT and 3/8 in. NPT ports, so confirm the thread in your case and in your radiator or cooler before you order. Some factory radiators use snap-in cooler connectors instead of a threaded port, and those need a separate adapter. If you are not sure what your transmission has, send us the year and VIN or the vehicle it came out of. Everything else we stock for this unit is on our 4L60E collection page.
If you are installing these on a freshly built unit, the 4L60E master rebuild kit with filter and a gasket and seal overhaul kit are the usual companions.
| Fits | GM 4L60E, 4L80E, TH350, TH400, 700R4, 200-4R; Ford AOD, 4R70W |
| Hose | 2 x 70 in., 6AN, 3/8 in. ID, PTFE liner, stainless braid, nylon cover |
| Fittings | 4 x 6AN to 1/4 NPT, 2 x 6AN to 3/8 NPT, 4 x 90-degree 6AN male-male |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
They are universal 6AN lines, not formed factory lines. They work on a stock truck if your case and cooler ports accept the included 1/4 in. or 3/8 in. NPT adapters. Radiators with snap-in connectors need a separate adapter.
PTFE resists swelling and softening from hot ATF, so the inside diameter stays consistent and the line lasts longer. The stainless braid also protects it from abrasion.
Use sealant on the NPT threads that go into the case or cooler. Do not put sealant on the AN flare connections, which seal on the flare itself.
The listing includes the 4L80E, TH350, TH400, 700R4 and 200-4R as well as the Ford AOD and 4R70W. Confirm your port thread size before installing.
Yes, especially after a failure. GM requires a cooler flush and flow test after transmission work because restricted cooler flow causes premature failure.
