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Not sure it fits your truck?
Our Wildwood, FL techs will confirm the right part for your build before you buy.
Call or Text (352) 722-5295Building the 48RE on the 2003-2004 5.9L Cummins piece by piece
The stock 48RE has a well-known list of weak parts: soft oil pump gears, babbitt bushings, cracking cast servos, accumulator pistons, the overdrive-direct snap ring, forward and direct drums with cast pistons, and the low/reverse sprag. The direct drum's cast-aluminum piston can crack, mostly on modified trucks, leaving you without third or reverse. The governor pressure transducer and solenoid wear out at any mileage and bring harsh shifts, limp mode and codes. Stock input shafts have snapped with as little as 500 rwhp behind a built Cummins. Heat ties it together: towing in overdrive with fluid over 260F triggers forced downshifts, which is why an auxiliary cooler is one of the first upgrades builders recommend.
What we carry
BD Diesel has the deepest lineup: Stage 1 through Stage 4 Build-It kits, with a Stage 4 version that includes a torque converter, a 48RE geartrain, billet input, intermediate and output shafts, a full manual valve body, a valve body with governor pressure solenoid and transducer, pressure transducer upgrade and adapter kits, a valve body electronics upgrade, the 48RE Tapshifter, short shift kits, Autoloc and Torqloc lock-up controllers, Xtruded auxiliary coolers and a universal cooler electric fan. ATS Diesel Performance adds a governor pressure transducer and a billet intermediate shaft. For cooling, Mishimoto has direct-fit and universal coolers plus radiator bundles, Fleece Performance Engineering a cooler and line kit, and CSF an OEM-style replacement cooler. DNR Customs supplies a flex plate install kit.
Fitment notes
Year ranges vary by part, so read each title. BD's short shift kits come in 1998.5-2003 and 2003-2005 versions, the Torqloc is listed for 1994-2004 Cummins trucks and the Autoloc for 1994-2005. Billet output shafts are 2WD or 4WD specific and come in 23- or 29-spline. Universal coolers are not truck-specific, so plan the mounting and lines; the Mishimoto MMTC-RAM-03TQ and CSF 20009 are direct-replacement coolers listed for 2003-2007 trucks. Verify by VIN before you order.
Frequently asked questions
Which Build-It stage do I need?
Builders rate 48RE builds by horsepower stage, so start from your power level and how much you tow. BD's Stage 4 kit is also sold with a torque converter. If you are past about 500 hp with lockup, make sure the build includes a billet input shaft.
Do I need an auxiliary cooler on a mostly stock truck?
If you tow, it is one of the first upgrades builders recommend. Fluid over 260F in overdrive triggers forced downshifts, and a deep finned pan plus an auxiliary cooler are the standard fixes. Mishimoto, BD, Fleece and CSF coolers are all on this page.
What causes governor pressure codes on the 48RE?
The governor pressure transducer and solenoid are known for short service life and can fail at any mileage, causing erratic shifts and limp mode. Raising line pressure above about 170 psi will also set codes. ATS replacement transducers and BD transducer upgrade kits are here.
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.