I have a manual transmission in a Ford Ranger with 240,000 miles and it has recently started making an intermittent grinding/grating noise. The conditions under which I have heard it are:
- Clutch is disengaged - If I re-engage the clutch (let off the clutch pedal), the noise goes away.
Transmission is in gear - If I move the stick into neutral while it is making the noise, it will go away.See edit below.
- Traveling at low speeds - Under about 5 mph or at a stop. At first it would only happen if I was moving at low speeds and go away as I stopped, but most recently it has continued to make the noise at a complete stop as well, though it does seem to slowly fade at a stop. It could be happening at higher speeds, but I don't notice it. I don't think it is loud enough that I would hear it above the road noise if it was happening.
- Sometimes - It doesn't do it every time these conditions are met.
The common scenario is that I'm coming up to a stop and I hold the clutch in and downshift into second/first above 10 mph. Then, as I continue to slow down with the clutch still disengaged, the noise will start around 5 mph and might vary in intensity until I've let off the clutch to accelerate. It seems like it is at its loudest just before I stop. Also, I wouldn't say the noise is loud, but it is obvious.
I was talking with a mechanic and he said if it only makes the noise with the clutch pedal pressed then it is most likely the throwout bearing, but I have been googling the symptoms and I've been getting conflicting answers. My understanding is that the throwout bearing would make the noise when the clutch is pressed, but in all the videos I've seen about a throwout bearing the person is walking around the car with their camera which means they are not pressing on the clutch.
Edit 23 March 2015:
I spent some time just trying to recreate the noise a paying attention to the conditions. I was only able to get it to do it a few times, but I noticed a few differences from my original conditions:
Transmission does not have to be in gear - I was able to move through the gears (including neutral) and it would continue making the noise, though it might vary in intensity.
Releasing the clutch makes the noise stop - I had it in neutral and let out the clutch very quickly (much quicker than if I was pulling away from a stop in first) and the noise disappeared immediately.
It happens while stopped - I had started to notice when I came to a complete stop, so as part of trying to recreate the noise I had the car in the driveway and put it in first and pushed the clutch in and out a little (not enough to move the car) and I was able to get it to make the noise once for about 20 tries.