2005 Transmission Clutch Release Rattling Noise Problem

2005 NSX. All OEM drivetrain. Only KW coilovers and NSX-R/other front suspension braces.

I will try to describe the problem as best as I can. The problem occurs when I'm just starting off in first gear and with engine under load. If I have to stop for traffic and push the clutch in the rattling noise happens. It's kind of like a rattle in a spray can except deeper (imagine a rattle ball inside a 5 gallon paint can if you could shake it fast enough). This also happens in car parks when going up to a higher story and me pushing the clutch in right at the top of a ramp (driving in 1st gear) it makes the rattle sound again.

Some background on the car since this issue has been on-going for a while now. In 2008 the car hit a curb with a fair amount of gusto which meant replacing some control arms, hubs and axles; the engine, transmission, frame rails, etc. were not affected. The wheel bearings are just now starting to make that howling noise but I don't think they're related to this rattling noise problem. Here is another odd item, when the car is cold, it's fairly hard to get into second gear from first. I imaging I have to re-bleed the clutch system to cure this issue but I'm fairly sure I've bled it correctly (will try again though). Once the car warms up it's butter smooth to get into second.

Could it be:

• clutch bearing?
• transmission cables? (We took the cable cover off to inspect when replacing control arms)
• something broken inside transmission?
• wheel bearings?
• axles?

I'm kind of stumped as to what it is but the noise is kind of embarrassing when taking people for a drive. If anyone has any suggestions as to what it could be let me know. Barring that I guess the transmission is coming out but I really would rather not do that with axle stands in a garage (I know it's been done).

In the videos below you will have to turn the volume up really loud to hear the sound (don't worry, there are no sharp or jarring noises like someone tapping a live microphone).

In the first video below, you can hear the noise at the 2 and 4 second marks
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In the 3 videos below, the sound can be heard from various angles. I am not pushing the brakes at all. I simply rev it up slightly then with the engine under load I push the clutch. It's almost like a metallic sound. Sorry for the shaky camera but the outside videos are filmed by my girlfriend running beside the car.
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My hearing is bad, so I'm having a hard time detecting the true nature of the sounds.
Generally, if its the release bearing, it will rattle any time you push in the clutch. It should be easily noticeable when you are standing still (in a garage for example) at idle and press in the clutch. Note that I just finished doing my clutch and had a problem with the release bearing being smooth (no rattling noise), but somewhat stiff compared to the new bearing. On cold days, or when hot from driving a few hours, I would hear a brief screech/squeal upon releasing the clutch as the bearing initially touched the pressure plate fingers. With just a few initial miles on the new bearing, etc, the screech is gone; I'll see if my bearing theory holds as it get more use.

To me (my bad hearing again), videos 3 & 4 sound more like bad wheel bearings or CV joints than clutch. Let's see what others think/hear.

As to bleeding the clutch hydraulics, I don't think that's the problem. If you can stand still with the engine running, push in the clutch, and shift into any gear smoothly and no gear crunch, the clutch is fully releasing. Not being able to do a 1-2 shift at speed is either synchros, trans fluid, or possibly the shifter cable adjustment. Are you using either the Honda "white cap" trans oil or the GM "cocktail"?

So, those are my guesses based on your description and what I could (almost) hear.

For the release bearing it is silent just sitting in the garage. I can't hear anything other than a slight squeak or 2 (just movement noises). When I get the car jacked up I'll listen closer under the car.

Not a bad idea to check the CV joints. If the boots aren't ripped and the joints aren't clicking how do you tell if they're bad?

I'm thinking it might be the synchro for 2nd gear unfortunately. However, I didn't know you could adjust the cables. I thought they were just a "bolt-on" type of thing in one position only. I'll pull the inspection cover off and have a look. Maybe I'll take a picture or two. I had Honda MTF fluid in there. I'm not sure if it was white cap or not. The whole bottle was black (including cap) and it said Honda MTF on it. In Canada it might be the same as the US white cap. I then switched to Amsoil Synchromesh and the shifting was a bit smoother but more or less the same thing. Could have just been the new fluid.

Thanks for the suggestions so far!

to me the noise sounds like what happens if youre downshifting to the wrong gear and the RPMS are too low for the gear/engine. (I know youre not down shifting but just the only time i have ever heard that sound). Have you tried higher RPMs? maybe come off the clutch a little slower?

How many kms on the single disk clutch? Hard to tell from the videos but sounds like clutch chatter, or you might have a disc spring thats fallen out broken or gone bad. Usually the on-set of not being able to shift gears usually means possible clutch on its way out or worn out. Throwout bearing usually howls not a knocking or chiping noise. Go over the suspension upper lower ball joints, end links etc see if something has come loose from your last series of repairs from the curb hit.

I had an internal leak on my clutch master on my '00 which was causing me the odd downshift and coming out of gear the shift lever would stick and need some force to get it out. Replaced all 3 items Master, slave and clutch line at same time and reset the free play we are good now. But I've never had an issue with the noise yours is making.

First off, I don't recognize that noise. That said, a couple of comments.

You note hard shifting when going into second when the car is cold. When cold, the 1-2 and 2-3 synchros on my 2000 are definitely sluggish. Once the gear box gets good and hot, this disappears and the shifting is very smooth. Based upon comments from others, I gather this is not uncommon for the 6 speed box. In fact, when I had my NSX pre purchase inspection by an Acura 'certified' NSX tech, his comment was that the 6 speed box is notchy and stiff compared to the 5 speed box. I am using Honda MTF. If (as you note) the stiff shifting goes away when hot' I would focus on something else.

As noted by Ftuhy, with the engine running and the car parked, if you can shift in and out of gears without grinding then air in the clutch hydraulics is not likely the problem. In particular, if you can get in and out of reverse without noise, then your clutch is not dragging.

The NSX (it seems particularly the 6 speed) seems to have a lot of drivetrain lash. This lash is most noticeable in first and second gear where engine torque braking is more significant. If you are in first gear at about 20 km/hr and you role the throttle on and off and get some clunking, then this is the more or less normal drivetrain noise. You can minimize the noise by smooth clutch release. However, if the noise just manifested itself recently, then its something else. I will admit that the sound on the video does not sound like the noise that occurs in my car if I am sloppy with the clutch release.

I will check the rear joints out again but at last oil change none were leaking and all seemed tight (me just grabbing the wheel and jerking it around). I guess my next real step is to take out the wheel bearings and while they're out I'll inspect everything such as joints and axles. As far as I can tell the throw-out bearing is not making any sounds but now I'm second guessing myself. Maybe some of the wheel bearing noise is the throw-out bearing noise. That really settles it for me. I'll do the wheel bearings first before speculating anything else.

Old Guy, your description of the cold sluggish 1st to 2nd shift is spot-on what is happening to mine. I also know of the drive train lash you and others mention. I can confirm it's definitely more lash than anything I've ever seen before but with smooth clutch control I can "make" it smooth. Back to the problem, I can completely eliminate the sound if I press the clutch slowly. I'll do the wheel bearings and see if that fixes anything else at the same time.

Before you spend money on the wheel bearings.

First off, bearing failure tends to result in a howling noise that is continuous while the bearing is under load. Not like the noise in your videos. I also thought I might have a rear wheel bearing noise. I took it into the local dealership and had them check it out last year when I had some other routine service being done. Their comment was not wheel bearings, your rear tires are cupped implying an alignment problem. I have Dunlop DZ 101 tires which seem to have a bit of a reputation for cupping. I don't like the tires (coefficient of friction similar to the casters on my desk chair!) so I am not going to spend $ to do an alignment on them and thus can't confirm the dealership's diagnosis. However, I don't think the dealership would pass on the opportunity to generate some revenue from a wheel bearing change if there was the slightest chance that the bearings were going south!

Just something to check out. Hate to spend the $ and time for a wheel bearing change and discover that the noise is still there.

99 rs said:

I will check the rear joints out again but at last oil change none were leaking and all seemed tight (me just grabbing the wheel and jerking it around). I guess my next real step is to take out the wheel bearings and while they're out I'll inspect everything such as joints and axles. As far as I can tell the throw-out bearing is not making any sounds but now I'm second guessing myself. Maybe some of the wheel bearing noise is the throw-out bearing noise. That really settles it for me. I'll do the wheel bearings first before speculating anything else.

Old Guy, your description of the cold sluggish 1st to 2nd shift is spot-on what is happening to mine. I also know of the drive train lash you and others mention. I can confirm it's definitely more lash than anything I've ever seen before but with smooth clutch control I can "make" it smooth. Back to the problem, I can completely eliminate the sound if I press the clutch slowly. I'll do the wheel bearings and see if that fixes anything else at the same time.

Click to expand...

im just curios if you did find out what was wrong ? i have the same "problem" well its not a problem but it is very anoying when driving on parkinglots and places lite that.

//magnus from sweden

cant tell much from video ,just for shi** and jiggles check axle nut torque, had a similar problem with another car .

The axle nut not being tight might be something to check out. When I went to undo my left axle nut it came off with little effort with the setup I have below. The right nut required a significant amount of force to undo. Sadly I don't think that's my problem (although it could have led to my problem).

Magnus85, I haven't really looked into the solution yet. I made 2 more videos of me just turning the axle by hand. I'll take another video with the rotor off as it's making a lot of noise in the background. I can hear the rattling most prominent just in front of the small part of the inner CV boot.












Videos:
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<iframe width="420" height="315" src="https://www.youtube.com/embed/XMyzJW4Edjc" frameborder="0" allowfullscreen></iframe>

it is exactly the same problem I have. I can check tomorrow after work if I can figure out what is haunting.
I will keep you updated if I find something

One key factor to diagnose this is to understand the "speed" of the noise. It is either wheel speed related or engine speed related. When you say it makes no noise sitting in the garage, that tells me it is a CV joint or axle bearing. I am not able to listen to the videos at this time, but think about the speed of the noise and that will guide you.

HTH,
LarryB

That sounds like a broken Differential but thats very unlikely to happen ... I would pull the driveshafts and inspect the inner joints. I hope for you that its just that.

some clunk from the transmission when you move it like you do in the last video is totally normal. there is some play in the gears. nothing to worry about.

what's really interesting is that your driveshaft moves up and down in that video indicating a bad CV joint.

Bernhard

99 rs said:

The axle nut not being tight might be something to check out. When I went to undo my left axle nut it came off with little effort with the setup I have below. The right nut required a significant amount of force to undo. Sadly I don't think that's my problem (although it could have led to my problem).

Magnus85, I haven't really looked into the solution yet. I made 2 more videos of me just turning the axle by hand. I'll take another video with the rotor off as it's making a lot of noise in the background. I can hear the rattling most prominent just in front of the small part of the inner CV boot.












Videos:
<iframe width="420" height="315" src="https://www.youtube.com/embed/TxV4Jj4fbKI" frameborder="0" allowfullscreen></iframe>

<iframe width="420" height="315" src="https://www.youtube.com/embed/XMyzJW4Edjc" frameborder="0" allowfullscreen></iframe>

Click to expand...

ok ,so it was loose , thats the scene of the crime , when this nut is not properly tightened two things begin to happen . the outside axle splines begin to move and the axle begins to hammer the cv joints .I have seen cv joints cracked because of this . Did you try to tighten it and see what happens? that noise dont sound good

you have found what causes the sound?

//magnus

bumping this thread. Any resolutions? I have the same sound after installing a new clutch/rebuilt transmission

Hey, my NSX has a new OEM clutch and a rebuilt transmission and I have the similair rattling sound when shifting from first to second gear at low speeds. My car rocks back and forth and there's a tok-tok sound.