Differential Fluid Service at Johnny's Automotive

Gear oil is the most forgotten fluid on most vehicles. There's no warning light for it, no dipstick on most axles, and no sticker in the windshield, so it usually gets changed after something starts making noise instead of before.

The oil in your differential is thicker and built differently than engine oil because the job is different. The gears in there slide against each other under enormous pressure, and the additive package in gear oil is what keeps metal from touching metal in that contact. Those additives get used up and sheared down over time and under heat. When they're gone, the oil still looks like oil and no longer protects like oil, and the next thing to wear out is a set of gears and bearings that cost considerably more than a fluid service.

Two Central Florida habits are hard on it. Towing runs axle temperatures up and works the additives harder than normal driving ever does. Water is the other one, and boat ramps are the classic case. A hot axle housing backed into the water cools quickly, and that pressure drop can pull water in past a seal or the vent. Water turns gear oil a milky tan color, and once you see that, the protection is already gone and the bearings have been running without it. If you launch a boat, cross water, or got caught in one of those flooded August intersections, tell us.

Your owner's manual sets the interval for your vehicle, and most list a shorter one for towing. If your differential is a limited slip unit, some require a friction modifier added with the oil, and leaving it out can cause chatter in slow turns. We check what yours calls for. When we drain it, the photo of what came out goes to your phone.