Three-piece braided stainless 8AN cooler line kit that replaces the rusted factory lines on 2003-2007 Dodge Ram 2500 and 3500 5.9 Cummins 48RE trucks.
On a 2003-2007 Dodge Ram 2500 or 3500 with the 5.9L Cummins and the 48RE automatic, the steel transmission cooler lines are a known rust point. They corrode under the clamps and at the bends, and the usual first sign is a drip of red fluid on the driveway or a wet line along the frame. This kit replaces the whole factory circuit with three braided stainless lines, so you fix every weak spot at once instead of splicing in a patch and waiting for the next pinhole.
The pump in the front of the transmission sends fluid through the torque converter and then out to be cooled. On these trucks that fluid leaves the case, passes through a heat exchanger, continues to the air cooler at the front of the truck, and returns to the transmission, where it feeds lubrication to the gear train and bushings. A Cummins pulling a trailer makes a lot of heat in the converter, and every bit of it has to leave through this circuit. If a line leaks, the level drops; if a line is kinked, crushed or blocked, flow drops. Either way the transmission runs hot and short of oil. Industry testing published by GEARS Magazine puts the minimum healthy cooler flow at about one gallon per minute, with 200 degrees F as the ideal maximum temperature and fluid life cut roughly in half for every 20 degrees above it.
Clean the lines and run the truck, then look for fresh wetness with a light along the full length of each line. Check the fluid level hot. If you suspect restriction rather than a leak, do a flow test: disconnect the return line, run it into a container at idle in Neutral for a measured time, and compare the result with the target. Our 48RE pump failure guide walks through that test and how to tell a weak pump from a blocked cooler. The 48RE Cummins problems guide covers the overheating and towing issues that make a healthy cooler circuit so important on these trucks.
Made for the 48RE in 2003-2007 Dodge Ram 2500 and 3500 trucks with the 5.9L Cummins diesel. The kit includes three lines (transmission to the heat exchanger, heat exchanger to the factory air cooler, and air cooler back to the transmission), two 8AN-to-NPT fittings for the transmission case, two hose barb adapters for the rubber hoses ahead of the cooler, and thread seal tape. Hose construction is a PTFE liner, stainless steel braid and a nylon outer cover. It is not for gas-engine Rams or the 68RFE trucks that followed the 48RE. If your truck has an aftermarket cooler, compare its fittings before ordering, or send us your year and VIN to confirm. Other parts for this unit are on the 48RE parts page.
| Transmission | Chrysler 48RE |
| Vehicles | 2003-2007 Dodge Ram 2500, 3500 with 5.9L Cummins |
| Hose construction | PTFE liner, stainless steel braid, nylon outer |
| Fittings | 8AN |
| Includes | 3 cooler lines, 2 x 8AN-to-NPT fittings, 2 hose barb adapters, seal tape |
2003-2007 Dodge Ram 2500 and 3500 with the 5.9L Cummins diesel and the 48RE automatic. It is not made for gas-engine Rams or for the 68RFE trucks.
Three braided lines (transmission to heat exchanger, heat exchanger to air cooler, air cooler back to transmission), two 8AN-to-NPT fittings, two hose barb adapters and thread seal tape.
Yes, the fittings on the heat exchanger are reused. The factory fittings come out of the transmission case and are replaced by the supplied NPT fittings.
They are tapered, so tighten them gradually until they stop leaking. Do not run them all the way in; that can crack the aluminum transmission case.
ATF+4, which Chrysler specifies for the 48RE. Top off after install, run the engine, check for leaks hot, and set the final level on the dipstick at operating temperature.
Yes. A leak drops the fluid level, which causes slipping and heat. A restricted line cuts cooler flow, and fluid life drops quickly as temperature climbs above about 200 degrees F.
