drivetrain

Differential Fluid Change - Rear

for 2007 Ram 3500 5.9L I6 Cummins · 4WD

Difficulty

Easy

Time

42 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 75W-90 synthetic gear oil to maintain proper lubrication and extend component life.

Warnings

⚠Differential fluid may be hot if vehicle was recently driven. Allow at least 30 minutes to cool.

⚠Used gear oil contains metal particles and contaminants. Avoid skin contact and dispose of properly at a recycling center.

ℹ️The rear differential cover on AAM 10.5" and 11.5" axles uses a rubber gasket, not RTV sealant. Inspect gasket condition during this service.

Tools required

3/8" drive ratchetEssential

3/8" or 1/2" drive breaker bar

10mm hex (Allen) bit or socketEssential

Drain pan (minimum 6 quart capacity)Essential

Hand pump or fluid transfer pumpEssential

Wire brush

Shop ragsEssential

Torque wrench

Vehicle jack and jack standsEssential

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

Parts

Differential fill plug gasket × 1 — Use OEM specification
Differential drain plug gasket × 1 — Use OEM specification

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 ground and engage parking brake
Raise rear of vehicle and support securely on jack stands rated for the vehicle weight
Verify vehicle is stable before working underneath
Locate the differential drain plug (10mm hex) on the bottom of the differential housing and fill plug (10mm hex) on the front or side face

Procedure

1
Clean differential plugs
Use a wire brush to clean around the fill and drain plugs to prevent debris from entering the differential when plugs are removed.
2
Loosen fill plug first
Using the 10mm hex bit and ratchet (or breaker bar if needed), loosen the fill plug approximately 1-2 turns but do not remove it completely. This confirms you can refill the differential before draining. If the fill plug is seized, do not proceed with draining until it can be removed.
⚠Always verify the fill plug can be removed before draining to avoid being unable to refill the differential.
3
Remove drain plug
Position the drain pan under the differential. The AAM 11.5" axle has no drain plug, so drain the fluid by loosening the cover bolts and carefully prying the cover loose at the bottom to allow fluid to drain. Allow the differential fluid to drain completely, which may take 10-15 minutes.
4
Inspect drained fluid
Examine the drained fluid for excessive metal particles, glitter, or unusual debris. Small amounts of fine metal particles are normal, but large chunks or excessive material may indicate differential wear requiring further inspection.
ℹ️Excessive metal particles in the fluid may indicate worn bearings, gears, or damaged components requiring professional diagnosis.
5
Clean and reinstall drain plug
Clean the differential cover and axle mating surfaces thoroughly of all old gasket material. Install a new cover gasket, then reinstall the cover and thread the bolts by hand. Tighten the cover bolts in a crossing pattern to approximately 30 ft-lbs.
6
Remove fill plug
Completely remove the fill plug and its gasket from the differential housing. Set aside with the old gasket removed.
7
Fill differential with gear oil
Using a hand pump or fluid transfer pump, add 75W-140 synthetic gear oil through the fill hole. If equipped with a limited-slip (Trac-Lok/anti-spin) differential, add the specified friction modifier additive. Fill until fluid begins to trickle out of the fill hole opening, indicating the proper level has been reached. The AAM 11.5" rear differential holds approximately 3.5 quarts.
ℹ️Fill slowly to allow air to escape and prevent overfilling. Proper level is reached when fluid just begins to seep from the fill hole.
8
Install fill plug
Wipe the fill plug threads clean and install a new fill plug gasket. Thread the fill plug into the housing by hand, then tighten firmly with the ratchet using moderate torque.
9
Clean and lower vehicle
Wipe any spilled gear oil from the differential housing exterior. Verify both drain and fill plugs are tight. Carefully lower the vehicle from the jack stands.