You're driving your QX60 home to Blackhawk, and a whine from under the floor climbs in pitch as the speed goes up. It drops away when you slow down, and the SUV still drives normally. On an all-wheel-drive QX60, one likely source is the transfer case, the small gearbox bolted beside the transmission that turns power toward the rear wheels. A transmission service doesn't include this small gearbox, so at Driven Auto Care of San Ramon, we start with its oil.

A Separate Gearbox With Its Own Small Fill of Oil

The transfer case on a 2014 to 2020 QX60 has its own oil, completely separate from the transmission fluid. It takes a thick gear oil, and the full fill is only about five-eighths of a pint. This oil can go many years without a change unless we service it on its own.

The gearbox turns any time the SUV is moving, and it sits close to the exhaust, so the heat ages the oil faster. With so little oil in there, even a slow seep from a seal leaves the gears short. Old oil turns dark and thick, and the gears and bearings start to whine as they wear.

Infiniti's own schedule for the AWD QX60 calls for an inspection of this oil at 10,000 miles or once a year. On the severe schedule, Infiniti calls for replacing the oil at that same mark. Fresh oil of the type Infiniti specifies keeps the gears and bearings in this gearbox cool and turning smoothly.

Is the Whine From the Transfer Case or Somewhere Else?

A whine that rises with road speed can come from more than one place. Worn wheel bearings and tires make a similar sound, and the rear differential can too. A noise that changes only when the transmission shifts belongs to the transmission, not the transfer case.

So our first step is the gear oil level, along with the color and anything metallic in it. Low oil means there's a leak, and on this gearbox the seals where the axle shafts enter it are a common place to find one. We then road test the QX60 and listen at each part of the driveline to place the whine. If the gearbox is noisy because of low or worn-out oil, we replace the leaking seal and refill it with the correct oil.

A Shudder in Tight Turns Points to the Rear

A different complaint shows up in parking lots. If the rear of your QX60 shudders or vibrates during slow, tight turns on dry pavement, the cause usually sits at the back of the SUV. The rear differential has an electronically controlled coupling that sends a varying share of power to the rear wheels. When that coupling grabs during a turn, the shudder comes up through the floor.

Mismatched tires on a QX60 cause this same shudder. Tires of different sizes or very different wear make the front and rear wheels turn at different speeds, and the coupling slips and grabs against that difference in every turn. So we measure all four tires before we look at the coupling. If the tires match and the shudder stays, the coupling is the part we test and replace.

What Driveline Repair Can Involve

When the gears in this gearbox have run low on oil for a long time, a fresh fill won't stop the whine, and the gearbox needs repair or replacement. Catching a leak while the gears are still healthy keeps the repair to new seals and fresh oil. During that repair, you can use one of our loaner cars or take a rideshare home.

Call Driven Auto Care of San Ramon at (925) 830-4701 about the whine or the shudder in turns. We'll check the transfer case oil and the driveline, then fix the part that's making the noise. Your QX60's all-wheel drive is then ready for the first wet roads of winter.