Front Dana 30 takes about 1.25 quarts of 80W-90, rear Dana 35 or Chrysler 8.25 takes about 2.5 quarts of 80W-90, and the Dana 44a with Vari-Lok takes the special Mopar 80W-140 synthetic — 2.5 quarts. Use the right fluid in the Vari-Lok rear or it won't engage.
Three rear axle options shipped on the WJ: Dana 35c (base), Chrysler 8.25 (V8 non-Quadra-Drive), and Dana 44a with Vari-Lok (Quadra-Drive and Quadra-Drive II). The front is always a Dana 30 with vacuum-disconnect. Knowing which one you have determines what fluid to buy.
How to identify your rear: look at the diff cover shape. Dana 35c has a 10-bolt round cover, Dana 44a has a 10-bolt cover that looks similar but the housing is larger (1.32" axle shafts vs 1.18"), and the Chrysler 8.25 has a different bolt count — 10 bolts but with a flat oval shape. Or: pop the cover plate inside the spare tire well and look for a 198-, 248-, or 247-style transfer case identifier (NV247 = Quadra-Drive II = Dana 44a Vari-Lok rear). When in doubt, look up the build sheet by VIN.
**Critical:** The Vari-Lok rear uses a viscous coupling that needs Mopar 80W-140 synthetic (part 5135681AA). Pouring regular GL-5 80W-90 in there will not destroy the diff immediately but will reduce coupling effectiveness over time. Don't substitute.
Drain procedure is the same for all three: pull the cover (remove all bolts except the top one, leave it as a hinge to drop the lower edge first), let the fluid drain into a wide pan, clean the magnet on the cover, scrape the old gasket or RTV off the housing and cover surfaces, and check the magnet for excessive metal — fuzzy is normal, chunks are bad. New gasket or a 1/8" bead of Permatex Ultra Black RTV around the cover (with circles around each bolt hole), let RTV cure 1 hour before refilling.
The fill plug is on the side of the housing — 3/8" square drive on most years. Fluid level is at the bottom of the fill hole. Use a hand pump or fluid syringe — gravity pour from above is awkward.
| Part | Vendor | Est. price |
|---|---|---|
| Valvoline 80W-90 GL-5 gear oil (1 qt) — front and most rears | Valvoline | ~$10 |
| Mopar 80W-140 synthetic Vari-Lok fluid — Quadra-Drive II rear | Mopar | ~$28 |
| Mopar Limited Slip friction modifier — if rear LSD whines on turns | Mopar | ~$12 |
| Differential cover gasket or RTV | Fel-Pro / Permatex Ultra Black | ~$12 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.