Replaces the block-mounted torque converter oil cooler on 2003-2009 Ram 2500 and 3500 5.9L Cummins trucks running the 48RE automatic.
Pink, milky or foamy fluid on the 48RE dipstick, or an oily film floating in the coolant overflow bottle, usually means one thing on a 2003-2009 Ram 2500 or 3500 with the 5.9L Cummins: the transmission oil cooler on the side of the engine block has started leaking internally. This is the replacement block-mounted heat exchanger with its mounting base, built to replace Mopar 68004317AA, 05086946AA, 05086946AB, 05191791AA and 68253200AA.
Fluid leaving the torque converter is the hottest oil in the transmission. On the Cummins trucks it is routed through two steel lines to this coolant-to-oil exchanger on the driver side of the block, behind the oil filter. Engine coolant flows through one side of the core and ATF through the other. In cold weather the coolant warms the fluid up quickly; under load the coolant pulls heat out. The cooled fluid then returns to the transmission and feeds the lube circuit for the bushings, gears and clutches.
Cooler flow matters a great deal on this family. Restrictions in the coolers, lines or drainback fitting are the most common flow problem in the RE transmissions, and they show up as converter clutch slip, delayed engagement and lube failures, not just high temperature.
Pull the dipstick on a cold engine and look at the fluid against a white towel. ATF+4 should be red and clear; strawberry-milkshake color is coolant contamination. Then check the overflow bottle for an oily layer. A cooling system pressure test with the transmission lines disconnected and capped will show whether coolant is crossing into the transmission side. For a restriction rather than a leak, measure flow at the return line: a healthy circuit should move at least about a gallon per minute. Our 48RE fluid leak guide covers the external leak points to rule out, and the 48RE fluid type and capacity guide covers what clean fluid should look like and how much goes back in.
Fits 2003 through 2009 Dodge Ram 2500 and Ram 3500 with the 5.9L Cummins diesel. The 48RE was the automatic behind that engine through 2007; check your build if you have a late cab-chassis truck. This is the engine block-mounted coolant-to-oil exchanger, not the air-to-oil auxiliary cooler in front of the radiator. Match the old unit and its Mopar number against the list above, or send us your year and VIN. More parts for this transmission are on the 48RE parts page.
Never install a fresh transmission on a contaminated cooler circuit. Debris and old coolant trapped in the exchanger will go straight back into the new unit.
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Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
2003-2009 Dodge Ram 2500 and Ram 3500 with the 5.9L Cummins diesel. It replaces Mopar 68004317AA, 05086946AA, 05086946AB, 05191791AA and 68253200AA.
The fluid turns pink, milky or foamy instead of clear red, and the coolant level may drop with no external leak. An oily film in the overflow bottle points to the same cooler crossing the other way.
Usually not. Coolant attacks the clutch frictions and converter lining, so most shops rebuild the transmission and replace the cooler together. A cooler alone is the fix only if the leak is external.
No. This is the coolant-to-oil heat exchanger that bolts to the side of the engine block. The air-to-oil cooler in front of the radiator is a separate part.
ATF+4 only. Fill with the engine running and check the level with the fluid hot and the selector in Neutral, since the new cooler and lines take extra fluid.
