Tranny noise as well

[Marty van den Bosch]

I just had my tranny completely rebuilt, but this noise has been getting worse...

Symptoms

Tranny noise - minor but constant unless clutch is depressed then no noise - sounds like a berring to me.
When I sit idling without depressing clutch - I get a constant noise.
When I coast in gear - same noise but much louder.
If I depress clutch when coasting - no noise.
If I have foot on gas - noise is minimal.
To me it sounds like the input shaft berring, but a new one was just put in.

What else could it be?
The quaife?
The TOB?

[Merlin Beerens]

sounds like the throw out bearing to me

[Mike Schmid]

Throw out bearing should only make noise when it's turning and it only turns when the clutch is in... From my experience I'd say input shaft bearing.

[trevor_Shiggs]

had the same symptoms on my civic and it was input shaft bearing.

[Mike Schmid]

You just have to think it thru.  

The engine is running and turning all the time, bad bearings only make noise when they're turning.

So you push the clutch pedal in and act on the master, the master acts on the slave, the slave pushes the clutch fork towards the pressure plate.  Now the static fork has to press in the fingers on the rotating pressure plate, it makes this interaction with the throw out bearing.  The only time that bearing turns is when the clutch is in.  When the clutch is in it also disconnects the engine from the tranny so the tranny internals will stop rotating as long as the car is stopped.  So, if it's bad it will only make noise when the clutch is pushed in.

When you let the clutch out in neutral the TO bearing moves away from the PP and stops turning.  The engine engages the input shaft on the tranny and spins it, because the tranny is in neutral the output side of the tranny remains stopped.  So now the TO bearing is stopped and the input shaft bearing is spinning.

Basically if the clutch is in and you have noise then the TO bearing is bad, if the clutch is out and you have noise the input shaft bearing is bad.  As a rule only one spins at a time.  However, if you get the car rolling and engage a gear then put the clutch in both will be turning, the engine will be turning the TO bearing and the wheels, via the tranny will be turning the input shaft bearing.  

Get the car coasting a good clip somewhere safe, kill the HVAC, stereo, and engine to quiet things down.  Now, with the clutch held in play with the shifter and change gears.  The engine is stopped and because of that so is the TO bearing.  If your input shaft bearing is screwed it'll change pitch when you change gears because the rotational input from the tires is relatively constant and the rotational speed of the input shaft is a function of the gear ratio.  You'll also hear a whirring as you engage the gears, that's the synchros and pretty normal.  When the input shaft bearing goes bad chances are it'll take out the input shaft seal too and you will find oil residue all over the inside of the bellhousing, let that go long enough and it'll take out the clutch.

[Scott Girvin]

Wow.....nice write up Mike.......but may I suggest this... could the noise be caused by the tob even with the clutch out?....maybe cause the fork pivot ball has been shimmed too far causing abnormal wear of the tob..thus making it spin while the tranny is engauged?

Reason I mention this is cause I too have a tranny noise...Ive tried pin pointing the prob with no success. Grumbling type noise while the tranny is engauged.....moving or not....and sometimes gets louder upon "harder" accel.

Not to hijack your thread Marty......maybe we have the same prob?

[Mike Schmid]

Yeah, good point Scott.  That could be if you jacked around with the dimensions.  If the fingers were lightly dragging on the TOB it would wear out in a hurrybut then it should really make noise all the time no?  Just change pitch as you put the clutch in.  

All I know is in my personal experience I've seen symptoms like that and it was a bad input shaft bearing 5/5 times.  That's not to say something else can't be bad, I just haven't seen it.  I forgot to mention another symptom of bad input shaft bearing is popping out of 4th, the other gears will stay in fine but it'll pop out of 4th.

[Scott Girvin]

yeah I would think that the noise would happen all the time....only reason why Im opting for the tob is because Ive had this noise twice on 2 different trannies...and have never had an input shaft seal leak.