6L80 Transmission Cooler 2010, new other (see details) and ready to install. Fits the 6L80. Ships fast from the USA.
If your 2010 Tahoe, Suburban, Yukon, Escalade, Silverado or Sierra with the 6L80 six-speed has red fluid on the frame rail, a crusty line along the passenger side, or a transmission hot message that showed up after the fluid level dropped, this is the part to look at. The listing name says cooler, but what you are buying is the GM transmission oil cooler line assembly, part number 25999418, the inlet and outlet pipe pair that carries fluid between the transmission and the cooler. It supersedes GM 25941147 and crosses to aftermarket 624-205. It is new, unused stock that may not be in original packaging.
The 6L80 generates most of its heat in the torque converter and in clutch packs as they apply and release. Hot fluid leaves the case through one of these pipes, runs forward to the cooler in the radiator, and returns through the other pipe to lube the geartrain. The pair is formed steel with crimped sections and clipped together along the frame, which is exactly where road salt and moisture collect on GMT900 trucks. Once a line seeps, the level drops slowly. GM's 2010 Tahoe owner manual is blunt about it: the only reasons this transmission loses fluid are a leak or overheating, and too little fluid can make it overheat. Low fluid lets the pump draw air, line pressure goes unstable, and the clutches start to slip.
Clean the lines with brake cleaner, drive the truck until it is fully warm and look again with a light. Fluid tracking from a crimp or a rusted section on the pipe itself points to this assembly. Fluid only at the radiator tank or the case fittings may be an O-ring or the cooler. If the truck has been running hot, check the fluid condition too. Dark, burnt-smelling fluid means heat damage has already started, and our 6L80 common problems guide explains how heat leads to the converter shudder and clutch failures these units are known for. Pump trouble can also show up as low pressure and heat; see the 6L80 pump failure symptoms guide.
Fitment data for 25999418 covers the 6L80 (RPO MYC) in 2009-2014 Cadillac Escalade and Escalade ESV, 2009-2013 Escalade EXT, Chevrolet Avalanche, Silverado, GMC Sierra, and 2009-2014 Chevrolet Tahoe, Suburban and GMC Yukon, with the 5.3L LMG and LC9 and the 6.2L L94. It is the inlet and outlet assembly for trucks without the heavy-duty transmission cooling option (RPO KNP). Trucks with KNP route their lines differently and need a different part. Because GM changed routing by engine, cab, drive type and cooling package, compare the bends and end fittings to your old lines, or send us the year and VIN before ordering. Every part we carry for this transmission is on the 6L80 parts page.
Release the quick-connect fittings with the correct disconnect tool so the retaining clips are not bent, and cap the ports while the lines are off. Route the new assembly in the original clips and keep it clear of the exhaust and steering. Push each fitting until it clicks, then tug it to confirm it is locked. Refill with Dexron VI only and check the level at operating temperature using the 6-speed procedure in your owner manual. If the transmission overheated or failed before the line was caught, flush the radiator cooler, because debris left there circulates right back. A fresh 6L80 filter and gasket kit is cheap insurance at the same time, and if you want the extra fluid capacity the deep aluminum pan kit bolts on while the pan is down.
| Fits | 6L80 2010 |
| Part type | Transmission Cooler |
| Condition | New Other (See Details) |
| Brand | OEM |
| Ships | From the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
It is the GM cooler line assembly, part 25999418, the inlet and outlet pipes between the 6L80 and the radiator cooler. It does not include a cooler core.
No. This assembly is listed for 6L80 trucks without RPO KNP heavy-duty transmission cooling. Check the RPO label in the glove box, or send us your VIN.
The listing data is tagged for rear-drive applications, and GM sometimes routes lines differently by drive type. Compare the bends and fittings with your old assembly or send us your year and VIN before ordering.
Use Dexron VI only. Add back what was lost, then check the level hot with the engine running using the six-speed procedure in the owner manual. Do not overfill.
Change the filter and fluid, and flush the radiator cooler if there is any debris in the pan. If the fluid is burnt or the truck now slips or shudders, have the transmission checked before towing again.
