2003-2004 Dodge 5.9L Cummins Transmission Parts

Where the 48RE on the 2003-2004 5.9L Cummins is weak

Builders who tear these transmissions down point to the same list: soft oil pump gears, babbitt bushings, an open-style filter that can cavitate, a low-volume pan, cast servos that crack, accumulator pistons, the overdrive-direct snap ring, forward and direct drums with cast pistons, and the low/reverse sprag. Add the converter's cast apply piston, which deflects during lockup, an intermediate band that stretches by 120,000-150,000 miles, and a governor pressure transducer and solenoid that can fail at any mileage. The Cummins was detuned behind the automatic to stay inside the 48RE's 560-570 lb-ft input rating, so any added power goes straight at these parts.

Service first, then upgrade

The 48RE takes ATF+4 only, about 4 quarts per drain, and its bands need periodic adjustment; 47RE and 48RE procedures overlap for 2003. Heat is the other enemy: with fluid over 260F in overdrive while towing, the transmission forces downshifts. That is why a deep finned pan and an auxiliary cooler sit right next to a lower-stall billet converter at the top of the upgrade list. From there, a rigid 727-style intermediate band, billet servos and accumulators, and a valve body with an upgraded governor pressure system handle more power. Overly rigid flex plates can balloon or break, so use a reinforced steel or SFI billet plate.

What we carry

BD Diesel supplies Stage 1 through Stage 4 Build-It kits, a 48RE geartrain, billet input, intermediate and output shafts, valve bodies including a full manual unit, pressure transducer upgrades, a 48RE Tapshifter, short shift kits, lock-up controllers, filters and Xtruded coolers. ATS Diesel Performance adds governor pressure transducers and a billet intermediate shaft. Coolers also come from Mishimoto, Fleece Performance Engineering and CSF. Deep pans come from XDP, PPE and Mag-Hytec, with a Mahle pan gasket. Flex plates are from XDP and BD, with a DNR Customs install kit, and fluid is from Hot Shot's Secret and Lucas Oil.

Fitment notes

Many parts here cover a wider span, such as 1994-2007 or 2003-2007, so check the years in each title against your truck. A short shift kit listed for 1998.5-2003 will not cover a 2004; BD offers a separate 2003-2005 version. Billet output shafts are 2WD or 4WD specific and come in 23- or 29-spline. Most of this page is automatic-transmission parts; if your truck has the NV5600 manual, note that it takes Mopar 4874464 fluid, 4.75 quarts. G56 parts do not fit 2003-2004 trucks.

Frequently asked questions

What should I replace first on a stock 48RE that tows?

Start with temperature and the converter. A deep finned pan and an auxiliary cooler keep fluid out of the 260F range where the transmission starts forcing downshifts. A lower-stall billet triple-disc converter addresses the factory unit's weak apply piston and small clutch area.

My 48RE shifts harsh and sets governor pressure codes. Where do I start?

The governor pressure transducer and solenoid are the usual suspects, since both are known for short service life. This collection has ATS replacement transducers and BD transducer and valve body electronics upgrade kits. Keep in mind that raising line pressure above about 170 psi will also set codes.

Do I need a billet input shaft?

If you run past about 500 hp with lockup, yes. Stock input shafts have snapped with as little as 500 rwhp. BD and ATS also offer billet intermediate shafts, and BD a billet output shaft, for trucks built to that level.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.