Differential Service

Drain and refill the rear differential with fresh 75W-90 GL-5 gear oil and limited-slip additive, inspect for leaks and wear.

Warnings

Tools required

Parts

• Differential drain plug washer × 1 — Mopar 6504005 or equivalent copper washer
• Differential cover gasket × 1 — Mopar 4338009 or equivalent
• RTV silicone sealant × 1 — Mopar 4318034 or equivalent gear oil resistant RTV

Fluids

• 75W-90 GL-5 gear oil — 3.5 qt
• Limited-slip differential additive — 0.125 qt

Preparation

1. Park vehicle on level ground and engage parking brake.
2. Chock the front wheels securely.
3. Raise the rear of the vehicle and support on jack stands placed under the rear axle tubes or frame contact points.
4. Ensure the vehicle is level front-to-rear for accurate fill level.
5. If differential was recently driven, allow 30 minutes cooling time.

Procedure

1. 1

   Locate and clean drain plug and fill plug
   Locate the drain plug on the bottom of the differential housing and the fill plug on the differential cover (verify exact location against factory documentation). Clean around both plugs with a wire brush and shop rag to prevent contamination when opened.
2. 2

   Remove fill plug first
   Using a 3/8" drive ratchet, loosen and remove the fill plug from the differential cover. This ensures you can refill the differential after draining. If the fill plug cannot be removed, do not proceed with draining.
3. 3

   Drain differential fluid
   Position the drain pan under the drain plug. Using the appropriate socket, loosen and remove the drain plug. Allow all gear oil to drain completely (approximately 10-15 minutes). Inspect drained fluid for metal particles, which may indicate excessive wear.
   ⚠Gear oil may drain with force initially. Position drain pan accordingly.
4. 4

   Inspect and reinstall drain plug
   Inspect the drain plug threads and magnetic tip (if equipped) for metal debris. Clean the plug thoroughly. Replace the copper drain plug washer with a new one. Thread the drain plug in by hand to avoid cross-threading, then torque to specification. Note: Copper drain plug washer — verify correct Mopar part number against factory parts catalog for 1992 Viper.
   Torque spec

   Drain Plug41 Nm (30 lb-ft)
5. 5

   Remove differential cover bolts
   Remove the differential cover bolts (verify count against factory documentation — Dana 44 typically uses 10) in a crisscross pattern starting from the top center and working outward. Keep track of bolt locations if lengths vary.
6. 6

   Remove differential cover
   Carefully pry the differential cover away from the housing using a plastic scraper at the RTV seam (do not pry at machined sealing surfaces). Remove the cover and allow any remaining fluid to drain into the pan. Remove and discard the old gasket.
7. 7

   Inspect internal components
   With the cover removed, visually inspect the ring gear, pinion gear, and differential case for excessive wear, scoring, or damage. Check the limited-slip clutch packs for wear debris. Inspect the magnetic drain plug area for abnormal metal accumulation. If severe wear is present, further diagnosis is required.
8. 8

   Clean mating surfaces
   Thoroughly clean both the differential housing cover mating surface and the housing itself using a plastic gasket scraper and shop rags. Remove all old RTV and gasket material. Surfaces must be clean, dry, and free of oil for proper sealant adhesion.
9. 9

   Apply RTV sealant and install gasket
   If the application uses a gasket, install it dry (or per manufacturer instructions); if it uses RTV-only sealing, apply a continuous 1/8" bead of gear-oil-resistant RTV to the cleaned housing mating surface, circling inside the bolt holes. Do not use both a gasket and RTV unless specified by factory procedure.
   ℹ️RTV must be applied and cover installed within 10 minutes before sealant begins to skin over.
10. 10

    Reinstall differential cover
    Position the differential cover onto the housing, aligning all bolt holes. Install all 10 cover bolts hand-tight. Torque the bolts in a crisscross pattern starting from the center and working outward to ensure even gasket compression.
    ⚠Allow RTV to cure for 1 hour before filling with fluid, or 24 hours before driving if using non-instant-gasket RTV.
    Torque spec

    Cover Bolts41 Nm (30 lb-ft)
11. 11

    Refill with gear oil
    Using a fluid pump or funnel with flexible tube inserted into the fill plug hole, add approximately 2.0-2.75 quarts of 75W-90 GL-5 gear oil (verify exact capacity against factory specification for the Dana 44). Add the limited-slip additive (typically 4 oz or one bottle) during filling. Fill until oil begins to seep from the fill plug hole, indicating proper level.
12. 12

    Reinstall fill plug
    Clean the fill plug threads. Thread the fill plug in by hand, then torque to specification. Wipe away any excess gear oil from the differential housing.
    Torque spec

    Fill Plug34 Nm (25 lb-ft)
13. 13

    Lower vehicle and check for leaks
    Remove jack stands and carefully lower the vehicle to the ground. After lowering the vehicle, inspect the differential cover, drain plug, and fill plug for leaks. Optionally take a short test drive, then re-inspect the sealing surfaces for any seepage.

Reassembly

1. Allow RTV sealant to cure for the manufacturer-specified time before driving (typically 1-24 hours depending on sealant type).
2. Dispose of used gear oil according to local environmental regulations.
3. Record the service date and mileage for maintenance records.

Verification

• Check all fasteners are torqued to specification.
• Verify no leaks are present at the differential cover, drain plug, or fill plug after the test run.
• Confirm gear oil level is correct by removing fill plug—oil should be at the bottom of the fill hole.
• Test drive the vehicle and listen for abnormal rear differential noise (whine, howl, or chatter during turns which may indicate insufficient limited-slip additive).

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