Rep Power: 0

Hi All,

I have a 94 Civic Si with 95k miles that recently lost 5th gear (discovered it was very low on fluid). Thought it would be easy to swap the entire tranny with a pick-n-pull replacement instead of opening the case.

Long story short, the new/used tranny installed fine but now I have a grinding noise that was not there before. The noise happens with the clutch disengaged (pedal out), goes away with the clutch engaged (pedal pressed), happens during acceleration, and goes away with deceleration.

Also, I (re)used the clutch fork and TOB that were with the original tranny.
Thanks!

 
Rep Power: 518

Technically, your terms are exactly backwards. The clutch becomes DISengaged when you push the pedal down.


Input shaft bearing(s) would be expected.

 
Rep Power: 0

thank you, that is why I posted!

 
Rep Power: 518

If it is the input shaft bearings, the pitch of the noise should stay consistent with engine RPM changes (because the input shaft turns at engine RPM whenever the clutch is engaged (foot OFF the pedal)), instead of varying pitch with with road speed or gear changes.


HTH

 
Rep Power: 0

Great, so when I coast downhill or to a stop sign and the noise goes away, that reaffirms your diagnosis?

 
Rep Power: 518

Not really....not without more data....hard to describe in typing LOL

Well, some of the changes-- louder during acceleration and quieter during deceleration and coasting-- are because of changes in loading and thrust and how the bearing has worn... but the pitch of the noise will still be consistent with the rotational speed (RPM) of the input shaft, and whenever the clutch is engaged (foot off of the pedal) that RPM will be the same as engine RPM.
Pitch may be different between accel or decel as the shaft and bearings move their positions, but changes in pitch under each condition should still be consistent with the RPM as above. Usually wear occurs under a lifetime of acceleration so that's when it's noisy, and fairly quiet during decel....but not always.

At a complete stop--- with the shifter in a gear and your foot on the clutch pedal, pushed to the floor--- the input shaft will not be spinning at all so there would be zero noise from the input shaft bearings ......but there would be zero noise from anything inside the transmission because nothing inside it will be rotating under that condition.


At a complete stop--- with the shifter in a gear and your foot on the clutch pedal, pushed to the floor--- there are two different bearings that would be in use and moving....those would be the throwout bearing and the pilot bearing.
If all is quiet at a stop like that (clutch pedal down and shifter in a gear), you can assume those two are not making the noise.