Rear-end Knocking Noise

[Joshdc]

Driving home from work tonight, the GTR started making a noise I havent heard before. From inside it sounds to be coming from the rear of the car like the exhaust is slightly bouncing up and down knocking into the metal frame. It only occurs while decelerating but its repetition is timed with the speed of the car so the faster I'm going the more often the noise goes. Almost like something builds up momentum and bounces up and down. It may also occur over bumps but the R33 is so loud I cant quite tell (and my hearing is subject to the placebo effect). The noise does not occur while accelerating or under brakes, gears and clutch position were irrelevant.

I jacked it up and started wobbling things trying to work it out but haven't found anything obvious enough to trigger my limited mechanical skills. Looked in the wheel arches for anything rubbing or stuck to the wheels but no. Checked all fluids levels were ok, nothing leaking (except airconditioning condensation), no eccesive knocking showing on the powerfc...

It's loud enough to concern me, I'm sure people driving next to me can hear it.

Any ideas?

Edited October 30, 2009 by Joshdc

[Dohmar]

Driving home from work tonight, the GTR started making a noise I havent heard before. From inside it sounds to be coming from the rear of the car like the exhaust is slightly bouncing up and down knocking into the metal frame. It only occurs while decelerating but its repetition is timed with the speed of the car so the faster I'm going the more often the noise goes. Almost like something builds up momentum and bounces up and down. It may also occur over bumps but the R33 is so loud I cant quite tell (and my hearing is subject to the placebo effect). The noise does not occur while accelerating or under brakes, gears and clutch position were irrelevant.

I jacked it up and started wobbling things trying to work it out but haven't found anything obvious enough to trigger my limited mechanical skills. Looked in the wheel arches for anything rubbing or stuck to the wheels but no. Checked all fluids levels were ok, nothing leaking (except airconditioning condensation), no eccesive knocking showing on the powerfc...

It's loud enough to concern me, I'm sure people driving next to me can hear it.

Any ideas?

do you have adjustable rear upper control arms? mine are noisy compared to the stock bushs+control arm

-D

[Joshdc]

do you have adjustable rear upper control arms? mine are noisy compared to the stock bushs+control arm

-D

Stock arms as far as I know, the bushs arent stock, but that was changed wtih the suspension a few months ago and hasnt made the noise before.

[Dohmar]

Stock arms as far as I know, the bushs arent stock, but that was changed wtih the suspension a few months ago and hasnt made the noise before.

check the subframe bushes maybe

-D

[kidafa]

Have you got coilovers? Sounds like the knocking they make when they are blown or on their way out... :S

[rhys5169]

pillow ball mounts? most coilovers after 10-20thou kms do em in

[PREISS]

diff

[MYCEF3]

I was thinking Diff as well!!!

Happened the the cef one day, was driving on one day n the diff was noisy! and then it got noisier then it went bang as i was doin a Ubolt! after had really loud bangs on excleration and deceleration the faster i went the quicker the bangs! Checked it out as i crawled home (everyone stareing) And found the diff was f**ked. Had to go out n buy a new diff

1.5 way LSD

Edited October 30, 2009 by MYCEF3

[PREISS]

Im drunk. Im also intoxicated. im drunk

[Joshdc]

Yeh I had new coilovers fitted about 5k ks ago so atleast they would be warrantable hopefully.

How do I check the pillow ball mounts?

Hope its not the dif... sounds freakin expensive

Why do you think dif?

[BIT SUS]

check ur exhaust mounting points....

[MYCEF3]

Yeah same i hope it isnt the diff as well!

If its youv looked at all the exhaust, coilies and other stuff that could knock or hit, the other is the diff (only coz the banging ur hearing)

Edited November 1, 2009 by MYCEF3

[Joshdc]

Woops I forgot to post the resolution.

Luckily I found the source before I lost a wheel...

Turns out i am an idiot and didnt tighten a couple of wheel nuts properly. Caused this noise for a good week of driving - all good now though.

Thanks every for the suggestions.

[DIOR 33]

wheel nuts. how funny are you, something i would over look