Clutch noise while clutch depressed (98 Nissan Frontier)

In my 1998 Nissan Frontier I had the clutch replaced at about 115,000 miles. That included a “clutch kit” which included a new throwout bearing. Currently, I’m at only 145,000 miles. Much of that is highway miles.

However, a noise has developed. It’s a whirring or humming that happens when the clutch is depressed (disengaged). The noise is not present when the clutch is released in any gear, including neutral.

My first guess would be the throwout bearing, but again, that was replaced only 30,000 miles ago, and plenty of highway miles. The original lasted as long as the original clutch.

My second guess would be the pilot shaft bearing. That was not replaced with the clutch. (So the shop says.)

Any other guesses or advice?

No matter the case, is it a problem if I leave it be? I can live with the noise if I know it’s not really a problem.

It could be either but I think that the throwout bearing is more likely. It might not have had enough lubricant when it was manufactured or had a defective seal. If the sound starts the instant the clutch is depressed past the friction point, its the throwout bearing and not the pilot bearing.

Mine (97 Nissan PU) has been making this noise for about 4 years now. Eventually it will fail completely and I will have to replace the whole clutch assembly, but it wont damage anything that isn’t going to be replaced anyway. I don’t rely on my truck as a daily driver so I can afford to wait.

Throwout vs. pilot bearing:

Offhand, it does sound like a faulty throwout bearing. If so, maybe the early failure is due to the TO bearing never fully releasing due to insufficient freeplay in the clutch pedal. Checking that should be part of the clutch job.

While it varies based on severity a faulty pilot bearing can often cause a gear gnash while going into reverse. If it shifts smoothly into reverse without difficult and no gnashing the pilot bearing is likely fine. The pilot bearing should also be part of a clutch job.

As to the ASE study guide I’m a bit surprised that they refer to packing it with grease and forcing it out with a dowel/hammer or cutting the pilot bearing out. There’s a special tool made for pilot bearing/bushing removal that will accomplish the job very quickly.

Took it to the shop. They couldn’t tell by listening (they say). Wouldn’t matter, since the labor for one job would be the same as for the other. They’d have to go in and at that point they might as well replace them both.

I’m probably going to put off the repair. Job was quoted as close to $700. Probably reasonable, but honestly I don’t want to spend that chasing a noise.