Weird Noise, not sure where from

[Pir0San]

So I've been driving my Z lately, and I noticed about a week ago, a weird noise was coming from where I had originally thought was the fan blower motor. It sounded like a leaf had fallen into the air vent, and worked its way to the squirrel cage, and was spinning along with the cage. The noise would come and go, so I didn't worry too much about it. Today I drove it down the road, and the noise got even louder, and seemed to only happen when the transmission was in gear. If I was at a stop, and revved the engine, no noise. But as soon as I engaged the clutch and the driveline began to spin, the noise would be evident. It seems to vary with engine rpm (but noise is not coming from the engine from what I hear) and sometimes goes away for no good reason. I haven't had a chance to take a look at it, since it's dark and all right now, but I did crawl under it for a few seconds, and it seemed like the transmission was leaking fluid from the rear output shaft seal since it was flung all around on the bottom of the car.

Tomorrow (as long as it doesn't rain) I was planning on checking my u-joints, and draining my tranny fluid to see if there were any metallic shavings in it, and refill it to see if that was the issue. I'm also probably going to get a rear output shaft seal, if the auto parts store carries those as well. The noise seems to be coming from the passenger side of the transmission tunnel, and now sounds like a metallic scraping. I'm not sure exactly how to describe it, but imagine what a leaf in the squirrel cage sounds like, but then turn that into a metallic noise.

If it's the transmission, I have a couple spares that I can try. I just don't want to do a tranny swap to find out the problem is even easier than I had thought.

[=Enigma=]

I was gonna say the throw out bearing at first but if that was the case, I believe it would ouly make noise, or at the very least be loudest while the clutch pedal is pushed in.

[Pir0San]

I thought of the throw out bearing, but the noise seems to go away when the pedal is pushed in. It only happens when the clutch is engaged. Thanks though!

[240ZX]

Maybe a worn out piolet bushing or main input shaft bearing?

Tom

[Arne]

Not pilot bearing, as there's no movement on that once the clutch pedal is released.

If it varies with engine RPM, suspect the input shaft bearing, needle bearings between input and main shafts, or the countershaft bearings.

If it varies with road speed, suspect the output bearing.

[RogerZ]

something in the tranny if you only hear it with the clutch engaged. tranny input shaft bearing seems to be the favorite from the posts I've read.