Replace Drive Axle Boots

Front-drive vehicles, many all-wheel-drive vehicles and some rear-drive vehicles have constant-velocity joints that connect the transmission to the drive axles and wheels. A front-drive vehicle will have four CV joints, each covered by a boot.

CV joints are covered by rubber or plastic boots that keep the joints lubricated and prevent dirt and water from getting in. If a boot tears, grease can leak out and moisture and dirt can get in. If left unattended, it’s only a matter of time before the joint fails from lack of lubrication or corrosion. When that happens, the whole axle may need to be replaced.

Drive axle boots often last the life of a vehicle and are not listed among items that need periodic replacement. They should, however, be inspected at least once a year, or more often on high-mileage vehicles or ones that see what manufacturers describe as “severe” service, such as off-road use or driving-industry conditions.

If a small tear is caught early, it may require only the relatively minor repair of replacing the boot and adding fresh grease instead of more major surgery. Many repair shops, though, will recommend replacing the entire axle if a boot is torn because there may be unseen damage to the CV joints and axle shafts that could result in other problems.

Outer boots (the ones closest to a wheel) are more prone to tears than inner boots. One indication of a torn boot is grease spots under the front axle or grease splattered on or around the inward-facing side of a wheel. Among the indications that a CV joint or drive axle has been damaged is a clicking or popping noise when turning, or vibrations at highway speeds.

Automatic Transmission Act Funny

This is a great question, but we must examine what “acting funny” means when referring to one’s drivetrain before recommending a course of action. Do any of the following seem familiar to you?

Slipping

When an automatic transmission seems to slip in and out of gear, or the engine revs up but the vehicle goes much slower than the engine seems to be running, it’s known as slipping. Sometimes the gears reengage harshly.

Shuddering

This is where the whole vehicle shudders and shakes while driving, as if it’s having a convulsion. It feels like you’re driving over rumble strips even if you’re on a smooth highway.

Neutral Drop-Out

A condition that feels similar to slipping, neutral drop-out is where the transmission drops into Neutral when the vehicle comes to a stop or while driving, typically at slower speeds. Sometimes when driving, the trans drops out of gear resulting in the engine racing up, and then either sliding — or banging — back into gear, or you step on the gas and the engine revs but the vehicle goes nowhere as if it’s in Neutral.

Heavy Drivetrain Vibration

This heavy vibration is felt throughout the vehicle under acceleration, especially when the drivetrain is under load, such as driving up a hill or pulling a trailer. Though many things can make a car vibrate, this type of drivetrain vibration will subside when coasting or idling.

What’s Causing This?

The potential causes behind these behaviors are many. The most common include leaking internal or external transmission seals; mechanical damage to the transmission and/or transfer case’s vital internal hard parts such as gears, drums, etc.; old, worn-out transmission fluid; improper fluid; electrical software and hardware glitches; worn drivetrain components; bad transmission and engine mounts.

What Can You Do?

Most of the causes listed above require a mechanic, certainly, but you can start by inspecting the color, consistency and smell of the vehicle’s transmission fluid. Low fluid level can cause the slipping described above.

Even if the vehicle is not doing any of the stuff above, if the fluid is brown or lightly dark, then it’s probably time for transmission service, essentially a transmission oil change. Like the engine, the transmission has a filter and oil (called fluid because it does more than lubricate) that needs to be changed at regular intervals outlined in your owner’s manual. If there’s no reference in your manual, then check with your mechanic.

If one or more of the symptoms described earlier are present and the fluid smells burned and feels rough or gritty between your fingers, then have a professional look at it, because more than simple service is required.

For the conditions above, we recommend transmission repair specialists who have access to diagnostic repair info that could lead directly to the cause of the problem, rather than muddling around in hit-and-miss fashion. They can run pressure tests, dye-leak tests and an electronic diagnostic scan of the drivetrain control module.

Diagnostic costs vary with the eventual verdict, but you can determine the likely cost of transmission fluid maintenance for your specific vehicle in your area using our fair-price estimator. After inputting your make, model and year, select the maintenance category and then the service called automatic transmission fluid/filter change.

Smell in Your Car

If your vehicle is giving off an unusual or sickening odor instead of that new-car smell, follow your nose and find the source of the aroma. Bad smells can lead to expensive repairs or health hazards and shouldn’t be ignored. Here are some common odors and their possible causes:

Musty: If turning on the air conditioner generates a musty smell, mold and/or mildew have probably formed in the air-conditioning system. Moisture naturally collects on the cold air-conditioning evaporator (a small radiator that carries refrigerant into the car’s dashboard) and it may be harboring mold. Running only the fan at high speed (with the air conditioning off) can dry the evaporator.

However, that doesn’t guarantee the problem won’t reoccur — especially if it’s being caused by a clog in the drain tube that allows water to drip out under the car. A musty smell also can be caused by carpets that get wet when water leaks into the interior.

Sweet: Antifreeze has a sweet, syrupy odor, and smelling it inside a car usually means there’s a leak somewhere in the cooling system. The source may not be easy to see. For example, the leak could be from a corroded heat exchanger (aka heater core), which is usually behind the dashboard. The leak could be in the form of steam that enters the cabin, producing the smell and potentially fogging the windows. Have this problem addressed, because breathing antifreeze isn’t good for you.

Burning: Oil could be oozing onto a hot part of the engine or exhaust system. It also could come from overheated brake pads and/or rotors — due either to aggressive braking, pads that don’t retract when you release the brake pedal or the emergency brake being left on while driving. On a vehicle with a manual transmission, the clutch plate could be worn or overheating from riding the clutch pedal. Leaves or other material in the engine compartment — sometimes imported by nesting rodents — also can burn on hot surfaces.

Rotten eggs: If you can smell rotten eggs or sulfur, your catalytic converter may have gone bad. The root cause could be an engine or emissions-system problem that made the converter overheat.

Rubber: The smell of burning rubber could be an accessory drive belt that’s slipping or getting chewed up by a broken pulley or hose rubbing against a moving part. An overheated clutch plate also can smell like burning rubber.

Electrical: Smell burnt toast? That could be a short circuit in an electrical component or overheated insulation. Take electrical odors seriously, because short circuits and overheated components are common sources of fire.

Gas: It’s normal to smell a little gas when a cold engine is first started because of incomplete combustion. If you smell gas after the engine is warm, though, the gas cap could be loose or the evaporative emissions control system — which is supposed to contain fuel vapors and recycle them through the engine — could be leaking or clogged. Even worse, gas could be leaking from the tank or another part of the fuel system. Always investigate gas smells you discover when your car is parked before starting the car and potentially igniting the fuel.

Rotting fruit: It’s probably what it smells like. Look under the seats for a decomposed apple or banana.