Help with Diagnosing Transmission Noises

Transmission Mechanic

When you’re diagnosing transmission noises, often the drivers input or description of the noise is the most helpful piece of information.

However, keep in mind that a noise complaint the customer thinks is an automatic transmission problem can actually be traced back to something else in the drive-line.

Things like a bad CV joint on front drive cars and universal joints on the drive-shaft for rear wheel drive cars can generate rotational noises.

Also keep in mind that front and rear wheel bearings and even some brake system problems like a binding caliper or brake pad that’s hanging up can generate a noise that seem to the driver like a transmission problem because the noise changes with vehicle speed.

Automatic Transmission Noises

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When you have eliminated all of the other possibilities and the noise is really coming from the transmission then you can focus on the root cause.

Start by paying a lot of attention to the speed and the conditions at which the noise is most evident. This is very important to nailing down the transmission problem.

What happens if you hear a whining or grinding noise that increases with the engine speed and remains present in all gears including park and in neutral? The most probable source points directly at the transmission front pump assembly. It rotates whenever the engine is running regardless of what gear the driver selects.

Nevertheless, if you’re diagnosing transmission noises and the sound is evident in all gears, but not when it’s in park or neutral then the most probable cause would be internal parts rotating in all of those gears.

On a front wheel drive vehicle the drive chain can cause noise such as this. In addition, transmission parts like the input shaft, its bearings and the torque converter can also create strange noises under these conditions.

Nailing Down the Transmission Noise

When you get to the point where you eliminated all of the easy stuff and you’re now searching inside the transmission for the cause of the problem, careful inspection and disassembling of the transmission will be needed to pinpoint the problem.

automatic transmission oil pan
Automatic Transmission Oil Pan

Fortunately, as you begin to take the automatic transmission apart you may run across signs of the problem. This can often begin when you remove the pan. You may find flecks of metal or even pieces of bearings or bushings lying in the bottom of the pan.

The material composition can help you identify problem areas instantly. Brass shavings point towards bushings, friction material and steel chips point to clutch packs and chunky looking metal chips point towards gears and planetary assemblies.

I have mentioned this before on many other pages, but often when having specific problems with an automatic transmission many other car and truck owners experience the same malfunction.

When mechanics diagnose transmission noises they check for technical service bulletins. In fact, it remains likely that other mechanics have already identified this sound and provide insight on what’s wrong with an automatic transmission of a particular year, make and model.

My Chevrolet Blazer Transmission Troubles

Case in Point: Pictured below is the 4l60E transmission from my 2004 Chevrolet Blazer. They had a problem with the sun shell breaking on a few model years. When this happens the vehicle loses reverse only and all forward gears work fine. General Motors dialed back the line pressure to take the stress off the defective part, but this didn’t help my Blazer.

4L60E Chevrolet Blazer Automatic Transmission

I didn’t even bother taking it apart. I purchased a re-manufactured unit with a 3 year/30,000 mile warranty and just swapped them out. Give this transmission noise page a bookmark or share with a friend.

Learn about common manual transmission noises like gear clash and sounds generated from broken rubber mounts.

Let’s hope if you hear some terrible noise, it turns into a simple repair. I can tell you that broken mounts sound much worse then the repairs needed to fix the issue.  For a short lesson on automatics and additional pages that cover specific problems visit my automatic transmission pages.

The complete workshop manuals available in PDF format provide excellent coverage for diagnosing and repairing automatic transmission problems. Some of my favorite content from that section covers the overhaul and testing process.

Symptom charts and ladder diagrams allow you diagnose many transmission problems using a simple pressure gauge. The manufacturer provides hydraulic tap locations in several areas to help dealership level technicians properly diagnose issues that can the car maker from expensive warranty repairs.

Use the manufacturer desire to save themselves major repair costs to your advantage. See if we have a complete workshop manual for your specific automobile here.

Discover what kinds of auto repair information we cover on the home page. Also take the time to review how to use this auto repair website to your advantage.