Drivetrain problems

[Joe]

Background: Gen 2 RB25det into a 1997 240sx. engine was an automatic but was given a manual flywheel(do not know if it is a rb20 or 25), used clutch and RB20 transmission with my clip. resurfaced the flywheel and put a new RPS Max full face clutch on. new throwout bearing. (did not change release bearing first time from the automatic to manual.)

about 3 weeks after finishing the swap i start to hear a noise that can only be described as a deep vibrating noise in higher rpm when shifting. it gets progressivley worse as i drive the car and at a certain point the car becomes undrivable. the clutch does not slip, only workslike a light switch, on or off. adjusting the pedal does not change anything, flushed the transmission, nothing. this was about a year ago, i was forced to park the car to finish school because i had no time to work on it

i moved home about 2 weeks ago because i graduated school, i swapped the KA back in for emissions, passed, had the RB back in a couple days ago. this time i removed the auto pilot bushing and put a real 5 speed one in thinking that could be the problem. after hunting down some wiring problems the car was running beautifuly. no issues. for about 30 minuets. then the noise comes back.

when sitting at idle, pushing the clutch, no noise. if i push the clutch then try to engage a gear i get this noise. low deep vibrating that follows engine speed. it does not affect my shifting. i can go into gear smooth as ever while it makes this noise then release the clutch and it goes away. this has happened in all gears, at almost all times. ive even had the noise while free revving at idle and pressing the clutch at a high rpm.

right now im extremly frustrated, and have no idea what this problem is. the clutch, flywheel, TOB all looked completley normal while i had the RB out from emissions and to install a manual pilot bushing because i thought that was the problem. im at the end of my rope with this problem, im about to just ditch the transmission and get a new clutch and flywheel. the right ones.

after driving it a little more today (another 45 minuets of street driving) ive got some more info.

it makes the noise in neutral when revving, sometimes. about 50% of the time, same with pulling away from a stop. not all the time.. almost every upshift under normal driving and "spirited" driving makes a quieter version of the noise. it has NEVER made the noise on a downshift.

sorry its so long, i kinda need to get all the information out there.

[s13sr20chris]

no noise on downshift and the noise does not affect the shift.that makes me think its not the synchros or anything like that.

noise is only when clutch is down sounds kind of like a TOB

but then it does it while free revving.

could be a bearing in the trans. how is the gear oil in the trans?

its a low frequency right? no like an exhaust rattle or something?

[Joe]

the oil in the trans is brand new, 75w-90. 2.5 quarts of it. and no its not an exhaust rattle haha, this is something in the transmission. i think ive narrowed it down to the input shaft bearing.

[s13sr20chris]

ok, just had to make sure. some folks need to be asked that stuff.