48RE Transmission Cooler 2003, new and ready to install. Fits the 48RE. Ships fast from the USA.
Finding red ATF on the frame rail or under the radiator of a 2003-2007 Ram 2500 or 3500 with the 5.9L Cummins? The factory 48RE cooler lines are a common leak point, and once they weep the fluid level drops a little every trip until the transmission starts to slip. Although this item is listed as a transmission cooler, what you receive is a replacement cooler hose line kit, as pictured: three black braided hose assemblies with crimped fittings, two barb connectors that join to the factory rubber hose in front of the cooler, two threaded adapters and sealing washers. It is a new aftermarket replacement kit and it does not include printed instructions.
The 48RE sends hot fluid out of the torque converter circuit to the cooler in front of the radiator, and the cooled oil comes back to lubricate the gear train and clutches. On a diesel that tows, this loop carries a lot of heat. If a line leaks you lose fluid; if a line kinks or the cooler plugs you lose flow. Transmission Digest's ATSG article on the 48RE notes that a restricted cooler is one of the known causes of an engine stall when the transmission is shifted into gear hot, alongside a bad pump. Low return flow also means less lube for the parts at the back of the case.
Clean the area with brake cleaner, drive until the fluid is hot, and look for the wet spot. Leaks often start right at the crimp or just inside the hose end ahead of the O-ring, so check the aluminum fittings on the cooler itself for damage too; a chewed-up cooler stub will leak with any new line. If the fluid is dark or the truck already slips, read our 48RE Cummins problems guide and the 48RE pump failure guide before assuming the lines are the whole story.
This kit is listed for the 2003-2007 Ram 2500 and 3500 with the 5.9L Cummins and 48RE transmission. The 47RE trucks before 2003 route their cooler lines differently, so it will not fit those. Line routing can also differ with an aftermarket cooler or a cab-and-chassis setup, so compare the hose ends with your old lines or send us your year and VIN to confirm. More parts are in the 48RE collection.
| Fits | 48RE 2003 |
| Part type | Transmission Cooler |
| Condition | New |
| 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 cooler hose line kit shown in the photo: three braided hose assemblies, two barb connectors for the factory rubber hose ahead of the cooler, two threaded adapters and sealing washers. The cooler itself is not included.
No. It is listed only for 2003-2007 Ram 2500 and 3500 trucks with the 5.9L Cummins and 48RE, and the earlier 47RE trucks use different line routing.
Usually only what is in the lines and cooler. Top it up with ATF+4 and check the level hot in Neutral. A full pan-and-filter service on the 48RE takes about 8 pints.
On RE-series units that is usually a pump or a restricted cooler circuit, and sometimes a stuck TCC switch valve or converter. Fix any collapsed or blocked cooler line first, then test further if it continues.
Basic hand tools and line wrenches are enough. No instructions are included, so take photos of the old routing before removing anything.
