4L60E Transmission Cooler 2002-2006

If your 2002-2006 GM truck or SUV with a 4L60E leaves red spots on the driveway, needs a quart of ATF every few weeks, or you found a line rusted thin while under it for something else, this is the replacement cooler line set for that job. The photo shows what you get: a set of formed steel lines with the rubber hose sections already crimped on, not a radiator-type cooler core. These lines carry every drop of fluid that leaves the transmission to be cooled, so a slow seep here eventually becomes a transmission problem.

What the cooler lines do in a 4L60E

The 4L60E has its two cooler fittings on the passenger side of the case. Fluid leaves through the converter circuit, travels forward through one line to the cooler in the radiator tank (and to an auxiliary cooler on tow-package trucks), then comes back through the other line and feeds the lube circuit that oils the bushings, planetaries and clutch packs. GM's cooler flow bulletin names the bottom case fitting as the feed and the top fitting as the return, and it warns that a restricted circuit leads to premature transmission failure. In other words, a pinched or leaking line hurts twice: you lose fluid and you lose lubrication flow at the same time.

Symptoms of a bad 4L60E cooler line

• Wet, oily residue along the frame rail or on the lines near the radiator
• Fluid level low on the dipstick with a dry pan gasket and dry output seal
• Swollen, cracked or weeping rubber at the crimped hose sections
• Shifts that flare or slip when hot, because low fluid drops line pressure
• A burned 3-4 clutch after a line or fitting lets go, one of the 4L60E's best-known failures

How to confirm it before you buy

Wipe the lines clean, let the engine idle until the fluid is hot, and look again; a pinhole or loose crimp often only weeps under pressure and heat. GM's own check procedure has you read the dipstick at operating temperature, roughly 180-200 F, so check level the same way before and after. Run a hand along each line where it passes clips and crossmembers, since that is where scale eats through first. If you are already chasing slipping or burned fluid, start with our 4L60E common problems guide so you know whether the lines are the cause or just one more thing to fix.

Fitment

This set is listed for the 4L60E in 2002-2006 applications. Within those years the line shapes change with chassis, cab and bed length, engine, 2WD or 4WD, and whether the truck has the factory auxiliary cooler, so year alone does not guarantee a match. Before you order, lay your old lines out and compare bends and end fittings to the photo, or send us your year and VIN and we will check it. For other parts that fit this transmission, browse our 4L60E parts collection.

Install notes

• Drain or catch fluid first; the lines hold more ATF than people expect, and the cooler circuit adds to total fill.
• Pop the case fittings with a line release tool and check the retaining clips. Sonnax documented a 2000 Chevrolet pickup that lost its 3-4 clutches when a worn clip let the top line back out of the case.
• Route the new lines through every factory clip so they cannot rub on the frame or exhaust.
• Refill with Dexron VI, idle in park, recheck hot, and inspect every joint after a test drive.

If the old fluid was dark or smelled burned, change it while you are in there. A pan with a drain plug, such as our 265-811 aluminum pan with drain plug or the finned aluminum pan, makes repeat drain-and-fills easy while the new fluid cleans the circuit.

Is this a radiator-style cooler or a line set?

It is a cooler line set: formed steel tubes with rubber hose sections, as shown in the photo. It replaces the lines between the 4L60E case and the radiator or auxiliary cooler, not the cooler core itself.

Will this fit my 2002-2006 Silverado, Sierra, Tahoe or Yukon?

It is listed for 4L60E 2002-2006 applications, but line routing differs by cab, bed, engine, drive type and tow cooler. Compare your old lines to the photo or send us your year and VIN so we can confirm before it ships.

Which fitting on the 4L60E is the cooler feed?

GM identifies the bottom fitting on the case as the feed to the cooler and the top fitting as the return to the transmission.

How much fluid do I add after replacing the lines?

Add Dexron VI to replace what drained out, then idle in park and check the dipstick hot, around 180-200 F. Top up a little at a time; overfilling causes foaming.

My fluid is burnt. Should I replace the lines anyway?

If the transmission has burned clutches, debris sits in the cooler circuit. Flush or replace the lines and cooler during the repair so that material does not get pumped into new parts.

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