View Full Version : Grinding sound while engine braking

02-05-2014, 11:53 AM
Hey guys,

Got myself a problem I haven't been able to figure out yet. A few days ago I started to hear a very distinct grinding sound when engine braking coming from the transmission area. I noticed it most in 2nd gear (probably because I've been doing a bunch of city driving) but have been able to reproduce the sound in 3rd and 4th as well.

Driving at 3000rpm, get off the gas and engine brake, grinding noise starts. Push the clutch in and the noise goes away. It also does not do it every single time, maybe 50% of the time and seems more likely to do it the more drastic the change is from acceleration to closing the throttle.

The only other thing that has caught my attention is a very subtle random pulse I can feel through the clutch pedal when idling.

Now, I did recently install the JHM solid shifter linkage and bushing. I see no binding in the linkage or contact with the transmission housing (the slim bolt head is facing the correct direction.) This problem also started a number of days after installing the bushing. There is an increased level of noise from the transmission with the bushing in place, but that noise remains constant and is distinct from the grinding I hear while engine braking.

I noticed that the down pipe hanger off the transmission was contacting the housing so I spaced it out, but the grinding persists.

I'm beginning to think it could be something more serious like a loose pressure plate or flywheel bolt. I'll put the car up on ramps again today and see if I can find anything else that is making contact where it shouldn't and try to get a good video of the sound. My dash camera picks it up but just barely.

Any thoughts?

02-06-2014, 09:25 AM

02-06-2014, 08:45 PM
backed out flywheel bolts wouldn't make a grinding sound while clutch was engaged, only while clutch was disengaged, and it would probably be pretty catastrophic.

Maybe a bearing in the transmission? Ever change your transmission fluid?

02-06-2014, 08:50 PM
Yeah, changed the fluid a few months ago when I replaced the speedometer magnetic ring.

02-06-2014, 08:50 PM
What'd you use?

02-06-2014, 08:51 PM
Redline MT90. Same fluid I've been running for 3 years.

02-06-2014, 08:58 PM
I'd have to say center diff. Press the clutch in, no more load on the center diff. This is just a shot in the dark though

02-06-2014, 09:09 PM
Redline MT90.

Glad to see that that works to summon you!

I'd have to say center diff. Press the clutch in, no more load on the center diff. This is just a shot in the dark though

Well, I did run rear tires that were too worn relative to the front for awhile. But I would think a failure like that would result in a gradual onset of increased NVH. This grinding sound came out of nowhere with no other indication. (Haven't bottomed the car out or hit any potholes, etc.)

If I would stop being lazy I'd go drive it and get a video of the noise...

02-06-2014, 09:27 PM
If Redline is correct, maybe put the car on jackstands, run the engine with car in gear, stop a front tire, see if you hear grinding?

My guess is transmission

My brain hurts from thinking about this and looking at diagrams for information, but I'll say what I'm thinking and you can take it or leave it:
I've never taken apart a transmission, but I'm under the assumption that 3/4th gear share synchronizers and bearings (fact check me?), so if the problem is only happening in those two gears, that would be my guess.

Now to decide if it is worth disassembling the entire transmission for a small grinding noise.

Check here for some pics inside the 01A, also a bad bearing.

02-06-2014, 09:37 PM
Thanks for taking the time to look into it. Thankfully (or not) the sound is not only in 3rd and 4th, it does it in 2nd as well.

On a side note, I would love to take apart a transmission simply for the sake of learning about it. I hope to save that for another day though.

I'm going to go try and get a video of the noise now.

02-06-2014, 10:44 PM
Well, I could not get the car to do it this time. Took it on a 10 minute drive and it didn't do it once.

I did however find a clip on my dash camera from a few days ago where you can hear it pretty well. I'll cut out out the useless parts and upload it soon. Yay dash camera.

02-06-2014, 11:24 PM
Here's a video of the sound.


02-06-2014, 11:32 PM
Does it feel like it's binding when it's making the noise?

02-06-2014, 11:34 PM
Get it on jack stands and replicate it in your garage.

02-06-2014, 11:39 PM
Nope, it doesn't feel like it is actually moving any different, doesn't want to pull in any direction, everything "feels" fine besides the grinding sound. I'm pretty sure I was able to feel it in the clutch pedal actually, this was a few days ago so I can't remember exactly. If I can get it to do it again I'll confirm that or not.

May have to do that Reno…I'll at least start by revving it while it's up on ramps to see if I can find anything contacting.

02-06-2014, 11:41 PM
Do you have all your transmission bell housing bolts in? Like top and bottom?

02-06-2014, 11:42 PM
Yep, haven't removed the transmission.

02-09-2014, 08:45 PM
Ooh, that doesn't sound good.

It has a repetitive rhythm to it, and it does not sound like it's wheel speed. So that leaves either driveshaft speed or engine speed. My guess is driveshaft. I would check to make sure it isn't rubbing on anything (heat shields, etc). Check the support bearing. Check the u-joint closely.

The deep tone of the noise suggest it is something large or heavy. I think if it were a flywheel bolt or related, it would get scary bad when the revs went up. But a driveshaft can cause problems at certain loads and speeds and "smooth out" at other speeds. So that's why I'm thinking driveshaft. Now, mind you I'm basing this off a single video, and I'm not a mechanic.

Good Luck.

02-10-2014, 06:47 AM
Kind of sounds like the flywheel or bell housing is shifting causing the ring gear to hit the inside of the bell housing.

Pulsing felt in the clutch pedal usually means a bad throw out bearing, but could also be caused by the PP being forced upward which then pushes the slave rod in/out.

Like others have said, it could be driveshaft related. But odd that it only makes noise when engine breaking and not while accelerating.

02-10-2014, 07:37 AM
The tail of the transmission will go up some during engine braking. So the driveshaft may be rubbing on something above it.

02-10-2014, 10:43 AM
Thanks a lot guys, appreciate your input. I'll get the car up on ramps today and check the driveshaft area out and see if I can take a peek through the clutch inspection hole to look at the ring gear.

Mad Cow
02-10-2014, 11:23 AM
How's your snub mount? I've had a similar noise but when accelerating because the snub mount fell apart and the fan was fitting the fan shroud.

02-10-2014, 11:45 AM
I've got a Neuspeed snub, didn't see anything wrong when I put the front end back on a couple weeks ago, but I'll take a look while I'm under there.

02-12-2014, 04:57 PM
Alright, got an update.

I took a peek through the clutch inspection hole and took the best picture I could. I don't see anything that catches my eye, but someone with more experience with clutches/flywheels may. I assume the shininess can be attributed to normal starting use.

http://i346.photobucket.com/albums/p439/blkA4alb-3/A4%20B5/DSC05947_zps64a08750.jpg (http://s346.photobucket.com/user/blkA4alb-3/media/A4%20B5/DSC05947_zps64a08750.jpg.html)

Also, it looks like I need to adjust my snub mount since it is pressing against the top of the housing at rest.

http://i346.photobucket.com/albums/p439/blkA4alb-3/A4%20B5/DSC05951_zpse7174000.jpg (http://s346.photobucket.com/user/blkA4alb-3/media/A4%20B5/DSC05951_zpse7174000.jpg.html)

02-12-2014, 07:15 PM
How are your transmission mounts? Check that driveshaft bearing. Did you get it on jack stands yet?

02-12-2014, 10:59 PM
Alright back with more news. I adjusted the snub mount so that the mount has 1/8" of clearance all around while the engine is idling. That seems to have helped with some of the vibration I was feeling, no idea if it affected my grinding noise though.

I popped off the driveshaft heat shield and my center support bearing does not look too good. The rubber is ripped and torn around the edge and it seems to be hanging low. I didn't notice any huge marks on the heat shield, but I did see a few scrapes. It also looks like the driveshaft has scraped something at some point. Pictures and videos show this better than I can describe it.

http://i346.photobucket.com/albums/p439/blkA4alb-3/A4%20B5/DSC05953_zps74f5d0a9.jpg (http://s346.photobucket.com/user/blkA4alb-3/media/A4%20B5/DSC05953_zps74f5d0a9.jpg.html)

http://i346.photobucket.com/albums/p439/blkA4alb-3/A4%20B5/DSC05952_zps912b7adc.jpg (http://s346.photobucket.com/user/blkA4alb-3/media/A4%20B5/DSC05952_zps912b7adc.jpg.html)

Bottom of the support bearing.

http://i346.photobucket.com/albums/p439/blkA4alb-3/A4%20B5/DSC05954_zps337c8aff.jpg (http://s346.photobucket.com/user/blkA4alb-3/media/A4%20B5/DSC05954_zps337c8aff.jpg.html)

Top of the bearing.

http://i346.photobucket.com/albums/p439/blkA4alb-3/A4%20B5/DSC05955_zpsd8067dc8.jpg (http://s346.photobucket.com/user/blkA4alb-3/media/A4%20B5/DSC05955_zpsd8067dc8.jpg.html)

After wiping the driveshaft down.

http://i346.photobucket.com/albums/p439/blkA4alb-3/A4%20B5/DSC05956_zpsa483a283.jpg (http://s346.photobucket.com/user/blkA4alb-3/media/A4%20B5/DSC05956_zpsa483a283.jpg.html)

Video of the bearing play.


02-12-2014, 11:33 PM
wull thurs yer problem. Good luck getting that bearing off, I hear it's a bitch. Someone posted a vid on instagram about it


"Used a wedge like a right triangle. It was a bitch to separate. Wasn't making much noise just vibrated the shit out of my car when I got on it. Definitely a pain in the ass job separating the driveshaft. Everything else is easy"

Also, wtf? is that an aftermarket drive shaft? Or are all of them carbon fiber?

02-13-2014, 05:54 AM
Early units are carbon fiber.

Can you drive the car without the shield installed? Maybe it's just rubbing on the shield.

02-13-2014, 08:30 AM
Early units are carbon fiber.

Can you drive the car without the shield installed? Maybe it's just rubbing on the shield.

Will early units fit on newer units? Lol

02-13-2014, 10:10 AM
Yes, I believe they will interchange just fine. But I've been told the Carbon Fiber unit is not any lighter than the later steel units.

Ah yes, here is the discussion on driveshaft differences from my pre-5mt-swap info gathering thread:

In post #40, Scotty from Advanced states that the steel units are actually lighter. Who knew?

02-13-2014, 10:33 AM
Early units are carbon fiber.

Can you drive the car without the shield installed? Maybe it's just rubbing on the shield.

I could, though I wouldn't want to drive without it for an extended amount of time, I'm sure it's there for a reason. I would try that if I could get the car to reproduce the sound on demand, but it hasn't done it for a few days now. I think what I'll try is to beat the heat shield in the areas where it looks like it was contacting the driveshaft and hope for the best. I'll plan on replacing the center support when I install a cat back since the exhaust has to come out to get the driveshaft out.

Side note, I thought the exhaust piping was round all the way back, but beneath the driveshaft it is flat on top.

02-13-2014, 10:35 AM
Side note, I thought the exhaust piping was round all the way back, but beneath the driveshaft it is flat on top.

Uhh...mines not.

02-13-2014, 10:43 AM
Yeah, the factory exhaust is flattened on top. It's subtle, as I recall.

Ooh, ooh! Here's a picture:


02-16-2014, 07:33 PM
Welp, the noise has now started occurring while accelerating as well, previously it was only heard during deceleration. With the car in neutral and clutch released (or depressed) there is no additional noise, so I think that rules out the throw out bearing.

I got to a stop sign and put the car in 1st, went to accelerate and heard the grinding over my music and felt it in the clutch pedal. Shifted to 2nd and got the same noise as I accelerated, same for 3rd. Got on the freeway and didn't hear much, maybe a slight increase in noise. Got off the freeway and heard it grind in 1st through 3rd. Parked the car for a few minutes and then drove it back home without it making a single noise.

With how far forward I'm hearing the noise (right at the shifter/transmission), it's hard for me to imagine the noise being caused by the bit of slop introduced into the driveline from the worn out center support. Though it seems like that is where I should start unless someone has a better idea. I'm due for a clutch replacement anyways, but don't have the cashola for that right now. Luckily I don't have to drive the car much (or at all if need be) right now either.

On what may be a related note, my engine has always made a pretty nasty sound when shutting down. It has sounded like this since I got the car four years ago so I never thought much of it, but maybe it has something to do with the new noise.


01-23-2017, 08:25 PM

Did you rule the noise down to being the worn out center support? I have the same issue with my 2006 S4. It only happens on deceleration presently.

If this is the case, how did you go about fixing it? Thanks for any help.

02-11-2018, 07:35 AM
Hey I'm having this same issue, how did you resolve it? My center bearing is fine though

Avant Nate
02-13-2018, 08:06 AM
I hate when you read a thread, and then the next day you realize your car is starting to do it as well.