48RE Planetary 2004

This is a used Mopar six-pinion steel front planetary with its ring gear, pulled from a 2004 Dodge Ram running the 5.9L Cummins and the 48RE. It suits a 2004 diesel Ram owner who has the transmission apart and found a cracked carrier, chewed pinions or a damaged annulus, or who lost forward drive while Reverse kept working. The unit is in good shape, with light rub marks on the tip of the annulus where the snap ring sat, which you can see in the photos.

What the front planetary does in a 2004 48RE

2004 was the second model year of the 48RE, the heavy-duty version Chrysler built for diesel and V10 Rams. Its front three-speed section is a Simpson gear train: two planetary sets sharing one sun gear, followed by a separate overdrive planetary in the rear housing. The rear clutch turns the front annulus in all forward gears. In first gear the front and rear sets work together, in second the front band locks the sun gear and the front set does the work on its own, and in third both clutches lock the whole gear train at 1:1. That makes the front planetary the hardest-working gear set in normal towing in second and third.

Symptoms that point to this part

• Truck will not move in Drive, 2 or 1 but Reverse is normal.
• A whine that follows vehicle speed and gets louder in second gear.
• Clunk or bind on light acceleration, or the transmission feels like it is dragging.
• Steel debris on the magnet when the pan is dropped, as opposed to clutch fiber.
• Second gear missing while first and third still engage, which shifts suspicion toward the front band, servo or the front set itself.

How to confirm before buying

The factory diagnosis charts for the RE family list a broken front planetary for the no-drive, Reverse-OK pattern and broken planetary gears for a drag or lock-up, with a reminder to look for debris in the pan. Those same complaints can come from a failed rear clutch or input shaft, so pull the pan first and run a pressure check. If you are chasing shift complaints rather than a hard failure, our 48RE Ram 2500 shift problems guide covers the valve body and governor causes that are far more common. For a heavier one-ton truck that tows, the Ram 3500 Cummins common problems article lays out the usual failure order.

Fitment

This unit came from a 2004 Cummins truck with the 48RE. ATSG lists the 48RE in 2003 to 2007 Ram pickups with the 5.9L diesel and the 8.0L V10. Before you install it, set it next to your old carrier and annulus: count the pinions (six here), compare the carrier hub splines, the annulus spline count, and the thrust washer tab holes. A five-pinion unit or a part from a lighter 46RE application may look close but is not what this is. If anything does not match, stop and send us your year and VIN. The full list of hard parts we carry for this transmission is on the 48RE collection page.

Install notes

• Clean the assembly in solvent and blow it dry, then check each pinion for smooth rotation and the pins for tightness. The factory manual calls for replacing the carrier if it is worn or damaged.
• Use new tabbed thrust washers held with petroleum jelly. The washers for the front set are the larger-diameter ones.
• Install the front planetary and annulus together, confirm the pinions are seated on the sun gear, then fit the planetary snap ring and measure geartrain end play. Correct it with a thicker or thinner snap ring.
• Inspect the matching drive parts at the same time. A worn 48RE input drum or damaged rear clutch hub can put the same marks on a new carrier.
• Refill with ATF+4. A 48RE shift kit is worth adding during the rebuild if your truck tows heavy and flares on the 1-2 or 2-3 shift.

Is this an original Mopar part?

Yes. It is a used Mopar front planetary and ring gear that was removed from a 2004 Ram with the 5.9L Cummins and 48RE. It shows light rub marks on the annulus tip where the snap ring sat.

Will a 2004 48RE front planetary fit my 2005 or 2006 truck?

Many 48RE geartrain parts are shared across years, but do not assume it. Compare pinion count and spline counts with your old part, or send us your year and VIN and we will confirm it first.

What else should I replace with the front planetary?

Replace the tabbed thrust washers and snap rings, inspect the sun gear bushings and the input drum, and flush the cooler. If the failure put a lot of metal in the fluid, the factory manual says the converter must be replaced as well.

Can a bad planetary cause a whine only in second gear?

Yes. In second gear the front band holds the sun gear and the front planetary carries the load on its own, so worn pinion bearings in that set are often loudest in second and quiet down in third when the gear train locks at 1:1.

Do I need to do any relearn after installing it?

No module relearn is needed for the planetary itself. Set geartrain end play during assembly, refill with ATF+4, and check the level hot in Neutral before the road test.

• 48RE Ram 2500 Cummins Shift Problems: Diagnosis and Fix
• 48RE Ram 3500 Cummins Common Problems and Fixes
• 48RE Cummins Transmission Problems: Failure Points, Upgrades, and What Actually Breaks
• 48RE Speed Sensor Symptoms: Output Sensor Failure and P0720