48RE Transmission Cooler 2009, used and ready to install. Fits the 48RE. Ships fast from the USA.
Leaking cooler lines are one of the most common reasons a 5.9L Cummins Ram with the 48RE starts dripping fluid or running hot under a trailer. This listing is titled transmission cooler, but the part is the factory steel transmission cooler line set from a 4x4 Ram 2500 or 3500 with the 5.9L Cummins and 48RE, Mopar part number 55056820AB. It is a used original part, not an aftermarket universal line, so the bends, brackets and end fittings follow the factory routing.
Fluid leaves the torque converter through the 48RE cooler circuit, travels forward through these lines to the cooler at the front of the truck, and returns to lubricate the gear train. Flow and restriction both matter. Sonnax notes that cooler restriction is by far the most common cause of converter clutch codes, lockup slip, delayed engagement and slow converter fill on the RE family, because back pressure in the cooler circuit pushes the converter switch valve off its seat. GEARS Magazine lists plugged lines and coolers among the top reasons these trucks overheat, with roughly one gallon per minute as the minimum healthy flow and 200 F as the ideal maximum temperature.
Clean the lines and fittings, run the truck to temperature and look for fresh wetness. For a restriction, measure return flow into a container at idle; well under one gallon per minute means a blocked line or cooler. Sonnax recommends temporarily bypassing the cooler and re-testing: if the lockup or engagement complaint goes away, the restriction is in the cooler circuit. Our 48RE pump and cooler flow guide explains the flow test, and 48RE Ram 2500 common problems covers the other leak points.
These lines carry Mopar number 55056820AB and are for the 4x4 version of the Ram 2500 and 3500 with the 5.9L Cummins and 48RE automatic. The listing dates the donor truck to 2009, but the 5.9L Cummins and 48RE pairing in these trucks ran from 2003 through 2007, so treat the year as unconfirmed and match by part number instead. Two-wheel-drive trucks and gas engines route differently. Compare the end fittings and bends with your old lines in the photos, check the tag number, or send us your year and VIN before ordering. More 48RE parts are on the model page.
If you tow heavy and want lines that will not crack again, the braided 48RE cooler line kit for the 5.9 Cummins is the upgrade path. If the truck already shows lockup slip after a heat event, a remanufactured 48RE valve body may be needed too. Background reading: 48RE Cummins transmission problems.
| Fits | 48RE 2009 |
| Part type | Transmission Cooler |
| Condition | Used |
| 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.
The lines. The listing title says cooler, but the part is the factory steel transmission cooler line set, Mopar 55056820AB, for 4x4 Ram 5.9L Cummins trucks with the 48RE.
No. This set is from a 4x4 truck. Two-wheel-drive trucks route the lines differently.
The 5.9L Cummins and 48RE were paired in the Ram 2500/3500 from 2003 through 2007, so the 2009 date is not reliable. Match part number 55056820AB or send us your VIN.
Yes. A restricted cooler circuit is a known cause of lockup slip and P0740 on RE-family transmissions. A bypass test confirms it.
ATF+4 only. Top it up and check the level hot in Neutral at idle, then recheck after a drive.
