Front & rear differential drain
We drain each differential completely — front, rear, or both — and let the housing empty fully. On sealed units without a drain plug, we pull the cover and scrape old gasket material clean before resealing.
Differential Fluid Service
Front and rear differential fluid changes — critical for 4WD, AWD, and rear-wheel-drive vehicles. Protects the gears and bearings that actually put your engine's power on the ground.
Why it matters
The forgotten gearbox under your truck.
Every rear-wheel-drive, four-wheel-drive, and all-wheel-drive vehicle has at least one differential — a sealed gearbox of hardened steel gears that takes power from the driveshaft and splits it between the two wheels on an axle. Trucks and SUVs with 4WD or AWD have two: one in the front axle, one in the rear. The transfer case on many 4WDs adds a third fluid-filled unit that works on the same principle.
Inside each differential, a ring gear and pinion mesh at a 90-degree angle under enormous pressure. The only thing between the gear teeth is a thin film of thick gear oil — and unlike engine oil, differential fluid has no filter. Every microscopic bit of metal worn off the gears stays in the fluid forever. Eventually that metal shears the gear oil, contaminates the bearings, and starts eating the ring and pinion.
Worn gear oil rarely warns you loudly. By the time a driver hears a whine from under the truck, the ring-and-pinion set is usually scrap — a $1,200–$2,500 job on most vehicles. A scheduled fluid change costs a tiny fraction of that. This service is especially critical for vehicles that tow, off-road, or drive in deep water or dust — all of which dramatically shorten the life of differential fluid.
What's involved
Drained, inspected, and refilled to spec.
A differential service is straightforward — but the details matter. The wrong fluid, the wrong friction modifier, or a missed magnetic plug inspection can turn a maintenance item into an expensive lesson.
Magnetic drain plug inspection
The drain plug is magnetic for a reason — it traps metal shavings between services. A fine powder is normal; chunks are not. What's on the plug tells us the health of the gears before we even refill.
Correct gear oil & viscosity
Differentials need specific gear-oil weights — usually 75W-90 or 75W-140 — and sometimes a GL-5 rating with limited-slip-compatible additives. We use exactly what the manufacturer calls for, not a generic gear oil.
Limited-slip friction modifier
Many trucks and performance rear-wheel-drives use a limited-slip or locking differential that requires a specific additive. Without it, the clutch packs chatter in corners. We add the correct modifier when the axle calls for it.
Transfer case fluid (4WD/AWD)
On 4WD and most AWD vehicles, the transfer case has its own fluid on its own schedule. We service it together with the diffs on most routine visits — same labor position, same mindset, different fluid.
Seal & leak inspection
Pinion seals, axle seals, and cover gaskets all weep as they age. With the differential drained, we inspect for seepage and let you know if a seal needs attention before it becomes a leak.
Signs it's time
When to come in.
Differential problems are usually invisible until they aren't. These are the symptoms that mean the damage is starting.
Whining or howling that changes with speed
Gear whine at 40–60 mph that goes away when you coast means the pinion bearing is loading and unloading. Often too late for a fluid change alone — but don't wait to have it looked at.
Clunk when shifting into drive or reverse
A sharp metallic clunk as you engage a gear often means excessive backlash between worn gears, or a failing u-joint upstream. Both need inspection before they leave you stranded.
Chatter or shudder in tight turns (limited-slip)
Trucks and performance cars with a limited-slip diff shudder in slow parking-lot corners when the friction modifier is exhausted. Usually fixed by fresh fluid with the correct additive.
Oily buildup around the axle or pinion
Fluid seeping from a pinion seal or axle seal shows up as a dirty film on the housing. Small seepage can wait; active dripping means the fluid level is falling and the gears are in trouble.
You tow, off-road, or drive through water
Hard use cuts differential fluid life in half or worse. If you've towed heavy, run trails, or forded water deep enough to wet the axle, the fluid is due — water contamination turns gear oil into a milkshake that won't protect the gears.
It's been 30,000–50,000 miles
Most manufacturers specify differential service on that kind of interval, sooner for severe use. If yours has never been done or you don't remember when, it's time to drop the fluid and look at the plug.
Protect what drives you home.
Differential fluid service is usually a quick job — most vehicles are in and out in under an hour per diff. Add the transfer case on a 4WD and it's still a same-day service.
Related services
What pairs with differential service.
Oil Change
Already under the vehicle for an oil change? It's the natural time to drop the diff plugs and check fluid condition — the labor's already paid for.
Transmission Flush
On 4WD and AWD vehicles, the transmission, transfer case, and differentials are all part of the same drivetrain. Servicing them together keeps the whole chain healthy.
Suspension Work
Worn u-joints, CV axles, and driveshaft carrier bearings cause the same vibrations and clunks that a bad differential does. We diagnose the whole driveline, not just the gearbox.