It started about a week ago. I would describe it as ticking or kind of like playing cards in bicycle spokes.

It is most noticable in first, second, and reverse in the lower rpm range though I think it's just drowned out by road noise in the other gears.
The ticking matches engine speed, not vehicle speed.
It only makes the noise under load when the car is in motion. If I am idle or coasting with the clutch in it is quiet. I also tried engaging the parking brake while in first gear to see whether it would make the noise under load while stationary; it didn't. Reving the engine in any gear with the clutch in is quiet.

I've read a bunch of threads on different bearing noises (input shaft, pilot, throw-out)... but none of the symptoms sounded exactly like mine.

Here's a link. It's not my car but this is the sound. You can hear it most clearly at about the 45 and 90 second marks.

http://www.youtube.com/watch?v=HSabp...eature=related

Some general information.
My car a manual with about 180,000 miles. The clutch was replaced at about 130k. I think I've ruled out timing chain slap but i'll mention that the chain and tensioners were replaced at about 140k.

Thanks,
Gavin

 

Most likely input shaft bearing, though it's odd that you can't hear it while the car is just idling (foot OFF clutch). Not pilot bearing since maximas don't have them, and not throwout bearing since the throwout bearing is stationary (not moving at all) when your foot is off the clutch pedal.

So if it is indeed a bearing noise, you're gonna have to open the trans up to fix it. Probably input shaft, though it's possible it's a diff or main shaft bearing problem. There are some more complicated scenarios I can envision that are causing this noise inside the transmission, but they all boil down to bearing replacement (for instance this could be the sound of your differential gear rubbing on the main shaft bearing because the differential bearings are bad and the diff is able to move slightly out of it's normal position. this is pretty common when diff bearings are worn. necessitating both diff and main shaft bearing replacement, even though the mainshaft bearing was not failing on it's own, it was ruined by the differential gear chewing up it's cage).

 

Thanks for the great info and insight, Nealoc187. I was hoping it could be something less intrusive like maybe a bad motor or tranny mount.