Deceleration rumble

Stuart123 · Dec 3, 2018

Hello All!
Noticed a new noise happening today. Happens about 20-30% of the time i let the car coast to a stop.
Haven't noticed when cold, definitely happening when hot.
Sounds like a rattling rumble.

Mainly in 3rd gear, sometimes in 2nd and 4th. Haven't noticed in any other gears. Tried to get it to happen in 1st for a while.
Best way i have found to replicate the noise is to manually select 3rd gear, rev up to about 2500rpm, then take my foot off and let it coast. Once it gets down to about 1500 it starts making the noise.
Doesn't really sound like exhaust shield rattle. Will not happen in neutral (stationary or moving).

My thoughts are it sounds like a toasted bearing.

My technical prowess are limited to basic stuff! mostly looking for feedback to help my mechanic diagnose the problem. He heard it today when he took it for a drive, but was unsure what is causing it.

I can take a video to record the sound if wanted. I think its loud enough to be heard, and happens enough that i shouldn't have to record to many video's trying to capture it haha.

Regards,
Stuart.

4ePikanini · Dec 3, 2018

if it only does it in certain gears then it's likely a gearbox issue. What's the mileage? Perhaps time for a fluid change.

Does the new shape treg also have the front diff bearing issue?

Stuart123 · Dec 3, 2018

Hello Pikanini,
Hoping its not gearbox! but i know its a possibility.
Done 101k kms.

A front diff bearing would line up with the direction the sound is coming from (Best i can tell hanging my head out the window, lol), and what i imagine it would sound like.

Cheers,
Stu.

4ePikanini · Dec 3, 2018

Drain the diff and put really thick GL-5 in there. If it gets better then it's the diff.

Stuart123 · Dec 5, 2018

Small update.
After my post 2 days ago, the noise has not returned.
I spoke to a VW specialist. He said he can't fit it in before Christmas unless urgent.
So unless the noise comes back, this will be put off until Jan.

Also, thicker diff oil is a good idea, cheers
If the noise comes back and this specialist can't fit it in, i'll ask my regular mechanic to do that.

Will update with anything that unfolds.

Regards,
Stu

Stuart123 · Dec 15, 2018

Another update here.
My mechanic said he didn't want to try a thicker oil as not to stuff something else up haha.
I took the car to an auto specialists who said he is very confident fully rebuilding the auto if needed. He said he doesn't think its the gearbox. But cant be sure without opening it up.

So, i have booked in to the local VW dealer for early January. It turns out that's the dealer who the previous owner also took it too for the majority of its first 100kkms.
So most likely no more updates until then. I did manage to get a recording of the noise, though as always its hard to hear with the phone recording. Its a louder rattly noise when hearing in live.

I'm still fairly new to using forums. Only started to get into it recently, if anyone wants to let me know how to post the small 115kb MP3 file that would be appreciated.

Regards,
Stuart.

Stuart123 · Jun 30, 2019

To update this.

Noise was completely gone the day of the inspection for the dealer, so I cancelled the appointment.
Received a reference to take it to A & B Automatic's (Dandenong, Melbourne). First try i dropped it off and it would not make a bleep for them. So they handed it back with confused faces.
I rebooked again and it actually made the sound for them, they had it for a the day and decided it was not the Auto. They think its somewhere else in the drivetrain.. possible tailshaft. But cannot be certain. Anyway, the guys there were very nice and didn't even charge me for their time ether days.

Guess I can try a diff specialist next to give me their thoughts.

Will update as I go... It such a loud disturbing noise. When its happening (on average 2-3 days each fortnight) I rumbles the whole way down my street as I'm just coasting down to my driveway, its embarrassing.

Regards,
Stuart.

Gnits · Jun 30, 2019

Because at an inspection they usually do not take anything apart, and your noise still seemed to go away, I doubt it would be related to gearbox, differential, etc, or anything else that is mechanically locked in such a tight way that some wiggling or prying by hand can't really cause any substantial movement in it. What I'd suspect instead is a bushing or bearing, that's only begun to degrade and/or was knocked partially out of place or into a weird angle by a heavy impact some time previously, and was popped back in place during the inspection. Just my two cents.

Deceleration rumble

Stuart123

4ePikanini

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4ePikanini

Stuart123

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