LS1powerhouse02

iTrader: (9)

Over the past few months I have slowly started hearing a noise in my transmission. It has gotten louder and louder it seems.

The noise is like a "rubbing/humming" noise. It only happens when the car is sitting still in neutral and you let the clutch out. Once you engage the clutch you can hear it "slow down" until it stops. I also noticed if the car rolls backwards (like out of a driveway) it makes the noise even with the clutch engaged. And the sound is equal to the speed the car is rolling.

I thought it was maybe the flywheel bolts backing out or something. But now I dont know. It sounds like it is coming more from the back of the tranny/shifter area.

So does anyone have an idea what it could be? The car has 112,000 miles and has a centerforce DF 12" clutch with new hydraulics that were all installed at ~85,000 miles. The tranny was rebuilt by GM at 36,000 miles.

Brent

thesource

iTrader: (60)

Just going off of what you are describing , I would start with the throw out bearing .

Z28M6TT

if it was the t/o bearing wouldnt it stop immediately when you press the clutch in, instead of slowing down? sounds to me like a bearing or something on the input shaft, cuz as soon as you put the clutch in the shaft would slow down to a stop. does your car have any leaks? maby you've been slowly leaking tranny fluid so now its making a bit of noise. i would pull the tranny fill plug out and stick your finger in to see where the level is at. a stupid problem is always better than an expensive one

thesource

iTrader: (60)

You're right , I must have read the post wrong . It might be something in the differential

LS1powerhouse02

iTrader: (9)

I check the tranny fluid about once every couple months. It is always full. No leaks at all.

When the car is sitting perfectly still and the car is idling with the clutch dis-engaged you can hear the noise. Then as soon as I engage the clutch it stops. It doesnt stop IMMEDIATELY but it only takes 1-2 seconds tops.

Now when I have the clutch engaged, the noise isnt there. If I roll down a hill with the clutch still engaged you can hear the same noise but it goes with the speed of the car.

I thought about the rearend but that doesnt make any sense when the car is sitting still.

Any ideas?

thesource

iTrader: (60)

With the car sitting still you can rule out the diff , the driveshaft and out put shaft bearing on the main shaft of the transmission .

You are sure the noise increases with vehicle speed and not the rpm of the engine ?

LS1powerhouse02

iTrader: (9)

the noise goes with the rpm when I actually engage the clutch and drive. But you cant hear it after about 1200-1300rpm. The only time it goes with the speed of the vehicle is when the clutch is fully engaged and it rolls backwards out of the driveway.

I replaced the TO bearing when I did the clutch swap but that doesnt mean it couldnt be that.

thesource

iTrader: (60)

So it does increase with the engine rpm ? How would you describe the noise ? A knock , whine , growl or squeel ?

LS1powerhouse02

iTrader: (9)

the noise is more of a whine/groan I guess.

It does increase with rpm im pretty sure. But you cant hear it once you let the clutch out and start accelerating. (im guessing from exhaust noise).

85MikeTPI

iTrader: (9)

Definitely odd.. Could be a pilot bushing/bearing. One of the internal transmission bearings as mentioned, but that would be a last resort check.

Could your starter gear be hanging out? unlikely, but just throwing out ideas..

Still wouldn't rule out a TOB. If something is sticking in it, it could gradually synch to speed and cause the gradual noise drop.

May just be time for some scheduled maintenance to check all the major parts, and replace all the little wear items..

good luck

Swamp Goat

I know this is an old thread, but hey, I searched and this guy has the same sound I do, so we both need the same answer I'd guess.

I will describe mine: light whine in neutral, clutch engaged. Bring the revs up, the whine rises in pitch. Disengage clutch, and I can hear it wind back down as the input shaft stops.

Driving, shift and let rpm fall with clutch disengaged I hear the same sound, falling pitch Speeding up, shift , whir, clutch engage and back on the gas I can't hear it, hit next shift, whir, engage,sound goes away (or is masked by engine/road sounds)..

Most noticable 1,2,3 gear during the clutch in part of shifts.
It is a whirring sorta wine, dependent on rpm.

This car is a 49k mile 2004 GTO. 402 stroker with about 520ft pounds on motor, occasional hit a 100 shot, gets close to 700ft #s.
Most of my driving is road course style, not hard core drag racing.
Gonna change the fluid this week and see if it looks odd.

thesource

iTrader: (60)

Does your noise go away in 4th gear ? Does it come back in 5-6 gear ?

Swamp Goat

Thanks for the reply Source. Let me get her outta the garage and try it on a super smooth road where I can build a little speed to see about the top gears.

Neutral ,1,2,3 it is equal in intensity and pitch is without a doubt dependent on input shaft speed.

I changed the tranny fluid at 29k when I swapped engines, all was okay, and put Valvoline ATF per gm spec in. No yabba-dabba-do fancy fluids every in the box.

LS1powerhouse02

iTrader: (9)

I cant really tell if mine is there during driving conditions. If it does I cant hear it.

I do know that I have a bad vibration that started about the time the noise started. The vibration is real bad when accelerating (especially in 5th and 6th gear). When I am cruising in 5th or 6th and let off the gas the vibration almost goes away.

I pulled the tranny a couple weekends ago and replaced the slave and TOB and nothing changed. I didnt have time to pull the pilot bearing b/c the car is my only car. But I could see the pilot and feel it and it seemed fine.

I have heard of people having problems with the tailshaft bushing going out and causing vibrations but that wouldnt have anything to do with the noise i dont think.

Thanks for the input "thesource".

Brent

Z28LS1camaroguy

iTrader: (3)

mine does the same thing, its a whining sound, but when i push the clutch in it goes away. Also if i let the clutch out slowly it doesnt do it, but if i let the clutch out fast it does it. Is that the throw out bearing???

99_Z_155

iTrader: (7)

Mine does this as well, but i attributed it to getting new tranny parts, a poly mount, and a textralia clutch. i put in a new pilot bearing, so i didnt think that was it. i was figuring it was the sound coming through the poly mount. sounds like a 60's medium duty bobtail truck gearbox. sound alot like gears meshing. my fluid was also ok. maybe thats what clutch chatter is, im not sure. it does sound similar to my 4.10s in the rear at highway speed, but sitting still and coming out of the tranny. push in the clutch and it goes away. i know its engine speed related because when my cam lopes, the sound surges as well. idk what it is, but it is slightly annoying.

Swamp Goat

Well, I got her out yesterday and confirmed a few things.
The sound is a nost noticeable when the input shaft is free-spinning down in neutral after a rev up then clutch pushed in.
The noise at shift is loudest when the synchros are being pressed into before it hits the gear.
Impossible to notice in 4-5th, 5th -6th shift.

Under the car, I found a little evidence of trans fluid leakage around the shifter gasket. Remember, the GTO uses a remote setup a bit different than Fbods.

On a hard pull through the gears (***** out), then lift in gear a noticable driveline wobble, almost like a driveshaft imbalance hits, but goes away after reapply power in normal drive.

I found a little fluid around the output shaft flange/shield, not sure if from the remote shifter weep or maybe a tailshaft bush/bearing/seal getting worn and letting the vibration happen on roll off and fluid leak.

Now that it's all clear as mud....

LS1powerhouse02

iTrader: (9)

mine has a little trans fluid seeping out of the tail shaft also. This is why I was thinking maybe it was a tailshaft bushing.......

Im glad to hear i'm not the only one having this problem though. I did a bunch of searching before posting this and didnt find one single thing.

Maybe I will try the tailshaft bushing replacement to see if it atleast fixes the vibrations. I dont know if it will fix the noise in neutral since the tailshaft turning has nothing to do with that.

LS1powerhouse02

iTrader: (9)

Bump still have the noise/vibrations