Hello I have a 98 ford ranger I just bought and it has been running very well. However this last week I started to notice a low and deep growl/ humming sound when I'm either in park or when I come to a stop and periodically when I'm at low speeds / rpm like 10 mph or below 1000 rpms. When this occurs it vibrates as well but you can feel it the most sitting in the back fold down seats. I'm not sure if this matters or if its because your basically sitting on the floor. I have been doing some research and I have made the conclusion it could be a faulty or bad toque converter due to related symptoms.
Any advice? What may be causing this? Is there any way to test my torque converter?