When you are diagnosing transmission noises often the drivers input or description of the noise can be the most helpful information. Also keep in mind that often a noise complaint that the customer thinks is an automatic transmission problem can actually be traced back to something else in the driveline.
Things like a bad CV joint on front drive cars, universal joints on the driveshaft for rear wheel drive cars, wheel bearings and even some brake system problems like a binding caliper or brake pad that is hanging up can generate a noise that may seem to the driver like a transmission problem.
When you have an eliminated all of the other possibilities and the noise is really coming from the transmission focusing a lot of attention to the speed and the conditions at which the noise is most evident is very important to nailing down the transmission problem.
If a whining or grinding noises is heard that increases with the engine speed and is present in all gears including park and in neutral the most probable source would be from the transmission front pump. This is because it rotates whenever the engine is running regardless of what gear is selected.
However if you are diagnosing transmission noises and the sound is evident in all gears but not when it is in park or neutral than the most probable cause would be parts that are internal and rotate in all of those gears. On a front wheel drive vehicle the drive chain can cause noise such as this. Also the input shaft and the torque converter can also create noises under these conditions.
When you have gotten to the point where you have an eliminated all of
the easy stuff and you are now searching inside the transmission for
the cause of the problem careful inspection and disassemble of the
transmission will be needed to pinpoint the problem.
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 that can help you identify problem areas.
I have mentioned this before on many
other pages but often when you are having a specific problem with your
transmission this may not be an isolated incident. When you are
diagnosing transmission noises it is also a good idea to check for technical service bulletins.
In fact chances are that other mechanics have identified this sound and
might provide insight on what is wrong with your automatic
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For a short lesson on automatics and additional pages that cover specific problems visit my automatic transmission pages.
Discover what kinds of auto repair information is covered on this site vist the home page from this page about diagnosing transmission noises.