So mdeezy and I are both stumped by this problem. It's a reciprocating sound when the clutch is out. Sounds like an input shaft bearing, right? Two things, though:

-The input shaft has NO play in it, and feels like butter when turned by hand.

-The reciprocating sound increases in pitch as I go through the gears. It's relative to speed, not RPM.

Any ideas?

 

You may not be able to feel this by hand. Bad bearings react very differently under load. If you have noise with the clutch engaged and the trans in neutral, you have a bad input shaft bearing.
Has to be, it is the only one that is rotating then.

 

Then why is the noise proportional to speed? The input shaft's pitch should match engine RPM, regardless of gear.

 

When I swapped my original differential for the Quaife a couple years ago, I also noticed this noise when in neutral, clutch engaged. Nothing has happened yet luckily.

 

have you changed TO bearings recently? what year is your transmission?

 

It's recently 5 speed swapped. The tranny is a 96, the TOB is brand new OEM Nissan.