Acceleration Rattle: Possible Causes

Imagine you’re driving down the highway one day, completely at ease. There’s no traffic and a nice, empty road stretches out in front of you. You’re well below the speed limit, so you decide to hit the gas a bit and enjoy the smooth sailing. Except, what if it isn’t as smooth as you’d hoped? If you start hearing a rattling sound when accelerating at low speed, it’s a sign that something’s wrong. Today, we’ll look at the different possible causes behind transmission acceleration rattle.

Acceleration Rattle Causes

Acceleration rattle can sound like buzzing, humming or grinding. Whatever the case, if this rattling occurs, it’s best to check for these culprits:

Low Transmission Fluid

If your vehicle’s transmission fluid levels are low and you’re hearing a grinding rattle, it means the metal parts inside the transmission aren’t getting enough lubrication. These metal parts rub up against each other a lot when the vehicle is on the road, and a lack of lubrication increases the chance of damaging these parts. Low transmission fluid levels can also cause the transmission to overheat, which wears out the parts even faster. Check your vehicle’s transmission fluid and top it up as needed. If you notice that the transmission fluid is draining out of the system too often, bring your vehicle to an auto repair shop for an assessment.

Inoperative Torque Converter

The torque converter is an internal engine component that sits between the engine and the transmission. It transfers rotating power from the engine to the wheels, multiplying torque when the rotational speed is very low. If your vehicle’s torque converter is acting up, you’ll notice a front-end rattle when accelerating and shakiness while driving at low speeds. An auto repair shop can help you diagnose and replace an inoperative torque converter as needed.

Broken Motor Mount

A motor mount, also called an engine mount or isolators, keeps the engine in place and absorbs the extra kinetic energy it produces, transferring that energy to other parts of the system. A broken motor mount can cause a metal rattling noise when accelerating at low speeds as the engine jostles around and hits other parts under the hood. If you notice a clunk or shudder when putting the transmission into gear or when hard accelerating on a rear-wheel-drive vehicle, it points to this problem. You can also look for scuff marks, scratches, and other signs of physical contact between the engine, transmission, exhaust system, and transaxle. Have a trusted mechanic replace the broken motor mount before driving anywhere. The last thing you want is for the mount to give up entirely.

Damaged Heat Shield

A vehicle can have multiple heat shields around its body, such as near the catalytic converter, engine bay, and exhaust manifold. If one of these heat shields becomes loose, then it might start vibrating in place, producing a rattling noise. If the heat comes off entirely, your vehicle might overheat or start giving off a burning smell.

Engine Accessory Issues

Some of the engine’s external components are positioned near the transmission, and if they start to malfunction, they might cause rattling or squealing noises in the area. Drive belt pulleys and tensioners are only two of these possibly problematic components. If you’re confident in your DIY abilities, you can check some of these components, but for anything too complex, head to an auto repair shop.

Faulty Wheel Bearings

Worn or faulty wheel bearings might cause whining, squeaking, chirping, and rattling noises when your vehicle accelerates. It’s a sign that the wheel bearings are either about to fail or have more than .002 inches of runout. If you hear these sounds from your vehicle’s wheels, try replacing the bearings.

Wheel and Tire Issues

If your wheels are misaligned or the tires are imbalanced, it can cause both shaking and rattling noises. Check your wheels for wobble and to see if the rims are bent. Change your wheels if you notice damage, and have an expert check your vehicle if you notice wheel misalignment.

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What To Do if You Hear Acceleration Rattle

While you can always investigate these issues yourself, acceleration rattle causes can be hard to pinpoint. Some problems are easy to handle, like faulty bearings or low transmission fluid. Other issues will require expertise and professional tools. If you can’t find the cause of your vehicle’s acceleration rattle, take it to the auto repair shop right away. It’s better to be safe than sorry.