The 4Runner front differential takes about 1.3 quarts of 75W-85 GL-5 gear oil and Toyota's recommended interval is 30,000 miles for severe service — the 1GR-FE platform has run reliably for two decades because owners actually do this.
The 1GR-FE 4.0L V6 4Runner uses a conventional open or limited-slip front differential. It's not part-time disconnect like a Wrangler — even in 2WD the front ring and pinion are turning, not driving. That means the fluid sees thermal cycling even when you're not in 4HI, and on a 4Runner that lives in Arizona heat or pulls a trailer, the front diff fluid breaks down faster than most owners assume.
Toyota's current spec is 75W-85 GL-5 gear oil. The OEM part number for the bottle on the parts counter is 08885-02506 (also packaged as 08885-02906 in some regions). Both are the same fluid. The older 4th-gen owner's manual originally listed 75W-90 for some build years, but Toyota's current TSB and the 2010+ spec moved everything to 75W-85 — using 75W-85 is correct across 2003-2024 4Runners. A name-brand synthetic 75W-90 GL-5 like Valvoline SynPower works fine if the parts house is out of OEM.
Capacity is 1.2 to 1.3 liters (1.3 to 1.4 quarts). The right approach is the same as every other diff: pump until it runs out the fill hole, then stop. Don't try to hit a specific number — vehicle level matters more than the spec sheet.
Both plugs are 24mm hex on most years (some 4th-gen use a 10mm internal hex). They're located on the front cover of the diff. The fill plug is the higher one; the drain plug is below it. Always crack the fill plug FIRST. A stuck fill plug after you've drained means a tow.
Service interval is the part most owners get wrong. Toyota's normal-service interval reads as "inspect" rather than "replace," which gets read as "do nothing." The severe service schedule — which applies to anyone who tows, wheels in dust, or drives in stop-and-go — calls for 30,000 miles. If you wheel in water at all, change it after every deep crossing; water in a differential is fast destruction.
| Part | Vendor | Est. price |
|---|---|---|
| Toyota OEM 75W-85 GL-5 differential gear oil (1 quart) | Toyota | ~$18 |
| Toyota OEM 75W-85 GL-5 (alternate part #) | Toyota | ~$18 |
| Toyota OEM fill/drain crush gasket | Toyota | ~$2 |
| Valvoline SynPower 75W-90 GL-5 (1 quart, alternate) | Valvoline | ~$13 |
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.