Differential Repair and Service for Trucks, SUVs and Cars In Missoula.

Differential repair covers the differential, the set of gears that lets the wheels on the same axle turn at different speeds while still sending power to both, along with the bearings, seals and gear oil that keep it running. That matters every time you turn, because the outside wheel travels farther than the inside wheel. Rear-wheel-drive trucks and cars have one in the rear axle, front-wheel-drive vehicles have one built into the transaxle, and four-wheel-drive and all-wheel-drive vehicles have more than one.

Inside the housing, the ring and pinion gears, the smaller side gears and a set of bearings all run in gear oil. That oil takes a lot of heat and pressure, and over time it breaks down and picks up fine metal from normal wear. If it leaks out or wears out, the gears and bearings wear sooner, and that's usually when noise starts.

The signs to watch for are a whine or howl that changes as you speed up or let off the gas, whining or grinding in turns, a clunk when you shift into gear or get on the throttle, vibration that comes on with acceleration, gear oil on the axle housing or the inside of a wheel, or a vehicle that feels like it binds or fights you in tight turns.

Four-wheel drive and all-wheel drive work hard around Missoula, between winter roads, gravel and off-road trips, and towing adds more load. That's real stress on the front and rear differentials. Running a part-time four-wheel-drive system on dry pavement is hard on the drivetrain too, since the front and rear axles can't make up the difference in speed in turns and end up binding.

We start by confirming the noise is actually coming from the differential. Wheel bearings, U-joints, tires and driveshaft problems can sound or feel a lot alike, and we'd rather sort that out than open up the wrong part. That means a road test, a look at the fluid and the housing, and checking for play and leaks at the seals.

Repairs range widely. Sometimes it's a fluid service or a leaking pinion or axle seal. Sometimes bearings or gears are worn and need to be replaced, which takes careful setup so the gears mesh correctly and run quiet. Either way, we'll tell you what we found, what needs attention now and what can wait, and what each option costs before any work starts.

Preventive fluid service is one of the simplest ways to help avoid a major drivetrain failure. Check your owner's manual for the interval and the right fluid, and expect a shorter interval if you tow or use four-wheel drive a lot. Some limited-slip differentials also need a specific oil or additive, so the right fluid matters as much as the timing.