drivetrain

Differential Fluid Change - Rear

for 1994–2007 Dodge Ram 2500 5.9L I6 Cummins Diesel · 4WD

Difficulty

Easy

Time

30 min

Tools

Steps

✓Fact-checked. Built from OLP's spec database, then independently fact-checked line by line with every correction applied. Master-tech sign-off by Chris Hackleman is queued. Cross-check torque values against the factory manual, and stop if anything looks unsafe. How our data is made.

This procedure drains and refills the rear differential with fresh gear oil to maintain proper lubrication and extend component life.

Warnings

⚠Gear oil may be hot if vehicle was recently driven. Allow differential to cool for at least 30 minutes before beginning work.

⚠Used gear oil may contain metal particles. Inspect drained fluid for excessive debris which may indicate wear issues.

ℹ️Ram 2500 4WD models used either AAM 9.25 or AAM 10.5 rear axles. Verify your differential type before ordering gasket.

Tools required

3/8 or 1/2 inch drive ratchetEssential

Socket set (10mm-19mm)Essential

Torque wrench (20-50 Nm range)Essential

Oil drain pan (6+ quart capacity)Essential

Fluid pump or squeeze bottle with tubeEssential

Wire brush

Gasket scraper or plastic scraperEssential

Clean rags or shop towelsEssential

Rubber mallet

Jack and jack standsEssential

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Parts

Differential cover gasket × 1 — AAM 9.25 or AAM 10.5 differential cover gasket (verify axle size)
RTV silicone gasket maker (optional backup) × 1 — Mopar or equivalent high-temp RTV

As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Fluids

75W-90 synthetic gear oil — 5.5 qt

Preparation

Park vehicle on level surface and engage parking brake
Raise rear of vehicle with jack and support securely on jack stands at frame rails
Verify differential is cool to touch
Locate differential cover on rear axle housing (flat plate with 10-12 bolts on back of pumpkin)

Procedure

1
Clean differential cover exterior
Use wire brush to clean dirt and debris from around differential cover bolts and perimeter. This prevents contamination from entering housing during disassembly.
2
Position drain pan
Place drain pan with at least 6 quart capacity directly beneath differential cover. Position pan slightly toward bottom of cover as fluid will drain from this area first.
3
Loosen differential cover bolts
Loosen all differential cover bolts in a crisscross pattern, but do not remove yet. Use appropriate socket (typically 13mm). Leave top bolts slightly snug while removing bottom bolts first.
Torque spec
Differential Cover Bolts35 Nm (26 lb-ft)
4
Remove lower cover bolts and drain fluid
Remove bottom and side cover bolts completely, leaving only the top 2-3 bolts loosely threaded. Carefully pry bottom edge of cover away from housing using scraper or pry bar to create gap. Allow gear oil to drain into pan. This may take 5-10 minutes for complete drainage.
⚠Gear oil will begin flowing immediately when cover is pried loose. Ensure drain pan is properly positioned.
5
Remove differential cover
Once fluid has fully drained, remove remaining top bolts and carefully remove differential cover. Tap gently with rubber mallet if cover is stuck. Set cover aside on clean surface.
6
Clean differential housing and inspect
Wipe interior of differential housing clean with shop towels, removing any old gasket material and debris. Inspect ring and pinion gears for unusual wear or damage. Small amount of metal shavings on magnetic drain plug is normal. Excessive chunks or glitter indicates potential problem.
7
Clean cover and mating surfaces
Remove old gasket material from both differential cover and housing mating surface using gasket scraper. Be careful not to gouge the machined cast-iron mating surfaces. Clean thoroughly with brake cleaner or degreaser and wipe dry. Both surfaces must be completely clean for proper seal.
8
Install new gasket on cover
Position new differential cover gasket on clean cover. Some gaskets are self-adhesive. If not, apply thin bead of RTV silicone to cover and press gasket into place. Ensure all bolt holes align properly.
9
Reinstall differential cover
Carefully position differential cover with new gasket onto housing. Thread all bolts by hand first to ensure proper alignment. Tighten bolts in crisscross pattern gradually in stages, then to final specified torque of approximately 41 Nm (30 ft-lbs); verify exact spec for your AAM 9.25 or 10.5 axle. This ensures even gasket compression and prevents leaks.
Torque spec
Differential Cover Bolts35 Nm (26 lb-ft)
10
Refill differential with gear oil
Locate fill plug on the differential (typically on the cover or side of housing; commonly a 3/8 inch square drive plug). Remove fill plug. Using fluid pump or squeeze bottle with tube, pump 75W-90 synthetic gear oil into fill hole until oil begins to drip from fill hole opening. Fill capacity is approximately 3.5 to 4.5 quarts depending on axle (AAM 9.25 vs AAM 10.5) but always fill until level reaches the bottom of the fill hole.
ℹ️Fill plug is at proper oil level height. Differential is full when oil just begins to seep from fill hole.
11
Reinstall fill plug
Clean fill plug threads and reinstall fill plug finger tight, then snug with ratchet. Do not overtighten the fill plug; torque to approximately 25 ft-lbs into the cast-iron housing. Wipe away any spilled oil from differential housing exterior.

Reassembly

Lower vehicle from jack stands
Check for leaks around differential cover after vehicle is lowered
If RTV was used, allow 1 hour cure time before driving

Verification

Start engine and allow to idle briefly, then check underneath for any gear oil leaks at cover gasket
Test drive vehicle in forward and reverse, then recheck for leaks at differential cover
After first 50 miles, inspect differential cover area again for any seepage
Mark calendar or maintenance log for next differential service in 30,000-50,000 miles or per manufacturer recommendation