Car Repair and Maintenance

6 Causes of Transmission Rattling Noise When Accelerating

transmission rattling noise when accelerating

You’re probably hearing a transmission rattling noise when accelerating. Well, this strange noise will unsettle any driver, making your driving experience poor. The solution, of course, is to find a fix.

If the noise rattles gently at first, you don’t want to wait for it to go away on its own. Maybe the noise will go away but it’ll return with many major problems. The rattle noise means you need to fix a problem, and this is possible through a DIY or by getting a professional to diagnose and identify it.

This publication is concerned about the possible causes you can detect/fix yourself or with professional aid. If the cause is technical, you obviously need professional services to permanently fix the problem.

transmission rattling noise when accelerating

Transmission rattling noise when accelerating

The common reasons why your car transmission makes a rattle noise when accelerating include the following:

1. Damaged engine mounts

Engine mounts are designed to help the engine of a car stay in place. Usually, they feature rubber and metal susceptible to wear and tear and need to be replaced.

The engine mount rubber can crack, become spongy, or just plain fall apart and liquids leaking onto it will accelerate the process. Also, power steering fluid, oil transmission fluid, or any leaking liquid draining onto the engine mount will speedily degrade it, according to Mobil.

When the engine mounts wear out, the car engine will move around while you driving. And when you accelerated, the engine comes in contact with nearby metal components under the hood, causing a rattling noise.

How to fix

a. Raise the engine

First, make sure the clearance against the firewall is okay before raising the engine. You don’t want to tear crimping AC lines, radiator hoses, or break distributor caps.

Use a jack to secure the engine, as well as wood blocks. Do not jack an engine directly by the oil pan to avoid bending and rupturing it.

b. Remove the engine from the mount

Remove the engine by loosening it from the mount bolts. Now, crawl under the vehicle and loosen the mount-to-frame bolts.

Raise the engine a bit with the jack, a little at a time, until you can remove the motor mount.

c. Install the new motor mounts

Make sure the new and the old motor mounts are the same. Move the drip or heat shields to the new mount. Thread the mount-to-frame bolts and lower the engine to simplify mount alignment.

d. Tighten the bolt

After lowering the engine, tighten all bolts. Note that cars with front-wheel-drive usually have third dog-bone motor mounts.

2. Broken heat shield

The heat shield is the component wrapping around the exhaust manifold of your vehicle. It stops manifold heat from getting to the components under the car hood.

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Unfortunately, the location of the heat shield means it is exposed to moisture and debris. It will easily attract rust, which builds up as particles eventually accumulate on the shield.

A rusty heat shield will break, causing transmission rattling when you hit the gas to accelerate, even at low speeds.

How to fix

A broken heat shield requires a replacement. Do the following:

  • Jack up and place it securely on the jack stands.
  • Loosen the heat shield bolts.
  • Remove the heat shield.
  • Install the new heat shield and tighten the bolts.
  • Lower the car and test it to make sure the shield is tight.

3. Malfunctioned fitting brake components

When you match the brakes to stop a car, that places the brake components under tremendous pressure. This means that the individual brake components will gradually shift if not fitted properly.

Thus, if one or more brake pads miss their anti-rattle clips, you’d get a rattling sound from the car.

How to fix

If your car brakes are responsible for the rattle noise, have a professional inspect it immediately to enhance your driving and road experience. You don’t want to drive around with faulty brake components —this can be fatal.

4. Faulty valve train

The intake and exhaust valves of your car can wear out or get stuck, causing premature ignition in the combustion chambers. A rattling noise is another common symptom you’d get when you accelerate. It should sound like glass bottles clinking together.

How to fix

The solution is to bring the car to a professional mechanic to check the valve. This is a more complex problem than what you may be able to fix yourself.

5. Insufficient transmission lubrication

The transmission in a car works as a gearbox, and it needs fluid that creates a thin layer between the moving parts. Thus transmission fluid prevents the moving parts from rubbing directly against one another. Generally, the transmission will not work properly if the lubrication is not sufficient.

A poorly lubricated vehicle transmission will cause the interior metal components to grind against one another, causing transmission rattling noise when accelerating.

By extension, this can result in the gear wearing inside the transmission, and will eventually render the transmission unusable.

How to fix

You need to check the fluid level to know if a replacement is necessary. If you believe that the transmission fluid level is low, insert a funnel in the transmission fluid dipstick hole and add transmission fluid. Add the fluid in small increments and continually check the fluid level until it level reaches the warm line.

Make sure not to overspill the fluid on hot engine components. Apart from changing the fluid, you want to be sure there’s no leak. Otherwise, the fluid will dry out again. Have a professional check the vehicle for leaks using specialized tools.

6. Worn exhaust components

If the exhaust components are worn, your car will develop a rattling sound when you accelerate. Components such as the exhaust gasket can get blown, the muffler can rust or corrode, and the catalytic converter can break, causing the rattling noise.

Not only will your vehicle produce rattles but will also alter the overall performance and fuel economy.

How to fix

The fix is to physically inspect if your exhaust system components are worn out. If so, have a professional look further and recommend replacements to stop the annoying rattles.

Conclusion

As expressed in this article, some of the problems, like checking and replacing transmission fluid, are things you can DIY. For the more complex problems, you want a mechanic to help out. Do not attempt to make replacements without the right tool and skills. Also, follow video guides or the owner’s manual for your specific vehicle model and model year to do the right thing.

This guide merely discloses possibilities. Your mechanic may deviate from the common problems mentioned here if they detect additional problems. Do everything possible to make your car roadworthy again.

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Bernard Juchli

Bernard Juchli is an experienced racer, mechanic and team owner who trusts Avon Tyres. Bernard is the lead driver and force behind his Big Dog Garage Race Team. He is the General Manager and Chief Mechanic of Jay Leno’s Garage. Bernard and his crew of seven are responsible for all repairs, restoration and fabrication of Jay’s incredible automobile and motorcycle collection.

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