Odd sound from driveline - videos added

billpatterson

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Hi there

I have a sound that I am looking into. Its kinda grinding, growly sound. It happens on lower speeds during deceleration. I thought it was the brakes but its coming through the shift lever hole so I think the driveline is the place to look. This includes many things including the exhaust.

So far I have checked,

- the brakes- rotors turned, new pads, calipers rebound, no chattering
- driveshaft flange bolts were tight
- centre bearing- new and seems fine
- u-joints- new, front seems fine, one axis of the rear u-joint is stiffer than the other axis/going to get the driveline shop to do a warranty check.
- tranny output shaft-driveshaft bushing- cleaned and greased
- guibo- new and bolts/nuts correct n tight
- tranny output shaft/flange- no leaks, no slop, output flange tight, tranny smooth
- driveshaft slip joint- cleaned and greased, nut tight
- no rubbing between shifter support/mechanism and guibo
- engine and tranny mounts- new and good

I have not yet checked,

- diff- input flange, pinion bearing
- exhaust- the rear flange of the front muffler has about 1/4" clearance to the driveshaft; there is very slight sign of a rub on the driveshaft but does not look like it would result in the sound. To test, I'll hang it a lil lower when reassembling.

Its a surprisingly long list to check. Any insight you have Forum is appreciated!? I feel it will be something simple.

Regards,
Bill
 
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Ohmess

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Hi Bill - we've been through this in our messages, but I thought I would post here so others can see:

My front muffler was hitting the drive shaft - sound was more pinging than the grinding you are hearing - which I discovered when I dropped the exhaust and saw a slight half moon area of wear on one of the seams on the center muffler. (Note I did not see this when the car was stationary; they only hit under load). Solution was to lower the muffler.

I also suggested checking CV boots and listening to the joints, but you have done this recently.
 

billpatterson

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Does the grinding match the gear you're in or the speed you're going?

I don't think anything is actually grinding; just a poor description of the sound; its more rubbing at a lower frequency at deceleration from lower speed.

I have begun reassembling the driveline as there was no physical evidence of things touching. No rubber dust, polished marks, missing material. I also went through the underside and checked each fastener for tightness; all were good. CV boots good too; a blown CV joint has its own sound. Center bearing is smooth. U-joints smooth and no slop. I don't think its anything internal (5 spd, diff, CV joints) as the sound is not muffled. I did disassemble, clean and grease the driveshafts front bushing; its lub was kinda old and thin; it was probably cooked when the driveshaft was modified for the 5 spd conversion. I'll reassemble the exhaust tonight and purposely hang it a bit low....

Cheers
 

billpatterson

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HI

Well...I have reassembled the driveline and reinstalled the exhaust. All components under the car including subframes, mounts, bushings were tight and clean. I was able to hang the exhaust a bit lower; the space between the rear flange of the front muffler is about 1/2" from the driveshaft. I took the 'bav' out for a test drive and have the same noise. I did a bit more testing; when rolling at low speed, in neutral, clutch depressed or engaged, and applying the brakes I get the 'rubbing sound'. Interestingly, I can modulate the sound by applying less or more pressure to the brake pedal. The sound is not a vibration or a chatter. Sorry...I'm kinda dumbfounded as all the deductive reasoning I can muster says 'its the brakes!'

I have never had this sound come from brakes. FYI the front rotors where machined, the rear rotors are new, new pads up front, old but healthy pads in the back. I do have new pads for the rear discs/I'll install them tonight/though its seems to be more from the font than the rear of the car.

Any more thoughts, Forum?

Cheers,
Bill
 

dang

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Pull up on the hand brake while the sound is occurring so you can cross that off the list.
 

Ohmess

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And a small rock in between the dust shield and the rotor can sound like a major problem even when it is not.
 

billpatterson

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Hey
Brakes are good; checked front dust shield, emergency brake function, rear caliper function, no rocks causing the banshee squeal. Though the sound can be modulated by applying light or heavy pressure on the brakes, it can also be heard when accelerating. The transmission runs smooth and quiet at speed and at idle with the clutch engaged. Given everything I've checked, I am going to focus on the centre bearing and differential. The sound is more like metal on metal and is from things that are turning. I will check the preload on the centre bearing, and drain the diff to check the condition of the oil and look into how to disassemble and take a look inside to see what if anything is causing this. More to come on this...

Thx for your insights, Forum!
 
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bavbob

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LOL. Dust shield does not move with the front rotor brake pads. I will have a closer look nonetheless to see if they are too close or contact the front rotors. THX

Bill
We don't have floating calipers but they are a case in which the dust shield moves relative to the caliper with brake application. Ask an Acura owner who learned this on tuesday!
 

TedS

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No mention of wheel bearings? True, all noises point to driveline but an easy check nonetheless. Brake pressure can be transferring weight on wheel bearings.
 

Ohmess

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When I found the bearing problem on my son's e34, I found it by pulling into a cul du sac, opening the windows, and doing slow circles first in one direction and then the other. I was able to perfectly reproduce the rumbling sound I had heard and confirm the need to replace the rear wheel bearings. Damn things lasted only 260,000 miles.
 

billpatterson

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THX

Please see links below for video of the sound. Its the cha-cha-cha sound during acceleration and the sshhhh sound during braking. Sorry for the poor descriptions of sound.

The sound is not gear dependent; tranny is practically silent when engaged to engine at any RPM.





Cheers
 
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billpatterson

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No mention of wheel bearings? True, all noises point to driveline but an easy check nonetheless. Brake pressure can be transferring weight on wheel bearings.
THX. Good idea! I checked the wheel bearings. Jacked, the fronts and rears spin freely with wheels on and off, no slop, no sound. When driving and cornering L and R, no additional sound.

Bill
 

Ohmess

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I just listened to your videos. Could your emergency brake be improperly adjusted so that it is on just a little bit all the time?
 
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