4L85E Transmission Cooler, new and ready to install. Fits the 4L85E. Ships fast from the USA.
If you run a 4L85E behind an 8.1L or 6.0L in a Silverado, Sierra, Express or Savana 2500/3500 and you tow, plow or haul at the top of the rating, heat is the thing that kills this transmission. This listing is an auxiliary transmission cooler kit: a stacked-plate cooler core, a long run of braided stainless hose, and the fittings, clamps and mounting hardware shown in the photo. It is the part to add when your temperature gauge climbs on grades, when the fluid comes out dark and smelling burnt, or when you are putting a fresh rebuild back in a work truck and want it to survive.
The 4L85E is GM's heavy-duty, five-pinion version of the 4L80E, introduced for 2002 under RPO MN8 and rated by GM for up to 650 lb-ft of engine torque. Under load the torque converter and the clutch packs turn a lot of energy into heat, and that heat leaves the case through the cooler lines. Fluid exits the transmission, passes through the cooler in the radiator tank, and returns to lubricate the geartrain. From 1997 on, the 4L80E family routes that return oil to the center support to feed center-gearbox lubrication, so cooler flow is not just about temperature on this unit; it is the lube supply for the planetaries and bushings. An auxiliary stacked-plate cooler added in series with the factory circuit gives that oil more surface area to shed heat before it goes back in.
Check cooler flow first. With the engine at operating temperature, a healthy 4L80E-family unit with 5/16 inch lines should push at least one quart into a container in 20 seconds, and most do it in about 10. If flow is low after the factory cooler has been flushed in both directions, the restriction may be in the cooler, the lines, or the pump's pressure regulator valve. Our 4L85E filter and pan service guide walks through that flow test and what the pan debris is telling you, and 4L85E common problems and fixes covers why heat is behind most of the failures on this unit.
This kit is listed for the 4L85E and is not tied to a single model year, because an auxiliary cooler mounts in front of the radiator and plumbs into the existing lines rather than bolting to the case. What you do need to confirm is space in front of your radiator or condenser, and how you will tap into your lines. GM notes that the return cooler line fitting on the 4L80 family is unique, and if you convert to standard inverted flare fittings it calls for adapter part number 8637742 for the transmission-to-cooler line and 24205178 for the cooler-to-transmission line. Installing the wrong fittings into the case can ruin the transmission. If you are unsure, send us your year and VIN before ordering, and browse every 4L85E part we carry.
| Fits | 4L85E |
| Part type | Transmission Cooler |
| Condition | New |
| Brand | GM |
| Ships | From the USA |
| Warranty | 1-year |
It is an add-on cooler that mounts in front of the radiator and splices into your existing cooler lines, so it is not year-specific. Check that you have room for the core in front of your radiator or condenser and plan your fittings. Send your year and VIN if you want us to confirm before ordering.
Possibly. GM states the return cooler line fitting on the 4L80 family is unique. To convert to standard inverted flare, GM lists part 8637742 for the transmission-to-cooler line and 24205178 for the cooler-to-transmission line. Never force a mismatched fitting into the case.
If the pan was full of clutch material or metal, the factory cooler is holding that debris. Flush it in both directions and verify at least one quart of flow in 20 seconds at operating temperature. If it will not flow, replace it, and an auxiliary cooler is a good addition on a work truck.
GM specifies DEXRON VI. A bottom pan removal takes about 7.7 quarts and a dry fill is about 13.2 quarts. Set the final level on the dipstick with the truck warm, running and in park.
No. A cooler slows the heat damage that causes slipping, but it will not repair clutches that are already burnt. If the 3-4 shift already flares, diagnose the clutches and valve body first.
