What's involved
What this repair actually is.
Differentials and transfer cases run on gear oil that breaks down with heat and miles, and most owners never think about it because there's no dashboard light for it. We drain the old fluid, inspect it for metal, and refill with the correct spec gear oil. AWD and 4WD vehicles have up to three units due at the same interval.
Symptoms
How you can tell.
- Passed 30K–60K miles with no record of gear oil service
- Faint whining from the rear on the highway
- AWD or 4WD vehicle with unknown service history
- Tow or carry heavy loads regularly
- Gear oil smell after long drives
If you delay
Worn-out gear oil lets the differential's gears and bearings wear metal-on-metal — a rebuild costs ten times what fluid service does.
Educational estimate. Real pricing depends on your vehicle, the inspection, parts availability, taxes, and shop rates. Use this as a guide while you shop quotes.
Related