# diff knocking ....!!! normal..?



## miragev (Apr 11, 2007)

right guys 

i have just fitted poly bushes to the rear subframe of my 32 gtr 
now during gear changes when i let the clutch out there is a knock from the back end
it sounds like backlash being taken up in the diff or maybe the diff is moving or possibly the prop is about to snap off..:nervous:...there was no knock before with the old nissan rubber subframe bushes
there was only a knock when letting the clutch out when reversing 
has anyone else noticed a knock after fitting polybushes ...that was not there before they were fitted...you see i have to drive back and forth right across europe next week and i'm shi**ing my self frankly...i,ve done this journey many times but...... not in a highly tuned prima donna of a tempremental gtr..


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## archaeic_bloke (Apr 22, 2008)

i wouldnt worry about it.

i recently fitted some alloy subframe bushes.. when i first drove the car like also thought my diff was about to explode but after a quick drive with my mechanic in the car he explained that the diff and subframe bushes... when replaced by a harder material (alloy) creates a huge amount of noise, because the body of the car now acts like an amplifier,... echoing the diff noise much more than before.

i hear noise when switching gears, wen comming off the accellerator at high speeds (anything above 100 kmh)

its normal...


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## miragev (Apr 11, 2007)

cheers mate 

and it's a knocking you have ?? not whining or anything like that..


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## archaeic_bloke (Apr 22, 2008)

lol ill be frank with you.. its really a whole bunch of different types of noises.
i would describe it like this:


when travelling above 100km/h and letting off the accel. its like the drive line is now pushing instead of being pushed so the noise is a thumping/loud engagement

when shifting its definitley a loud "clunk" just one then the driveline picks up the slack again..

when turning its a different noise

under accell i hear a slight buzz.


lol honestly theres so many noises but all is fine, its just cause you fitted those new bushes... the more stiff they are, the better the car handles but the noiser it will be too..


its all normal mate. 


the best way to test is to put the car through its paces i found.. my mechanic convinced me its normal by showing me the cars new handling abilities too.

toss it around in second gear from side to side. confirm that you diff sstill locks up.. get some power slides going...

youll see its all good!

how do you like the new bushes?

personally i REALLY love the feel


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## miragev (Apr 11, 2007)

i love how the car handles
i already have all adjustable suspension arms... all rose jointed throughout... tein ha coilovers (hard as hell) it's like driving a gokart and it bumps and bangs like crazy all ready...it was just the noise thats all ..all of a sudden a banging from the diff on gear changes .. ...you know how it is i kept think did i tighten the prop correctly... is this loose is that loose etc...


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## archaeic_bloke (Apr 22, 2008)

lol whats funny is i have the exact same set up as u suspension wise too! lol

so i know EXACTLY what ur saying brotha.

i too have fully adjustable FUCA, tension rods, RUCA etc.. and also Tein HA coil overs! LOL

and your right, i love the handling on the car...

best of luck!


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## Major_Sarcasm (Jul 28, 2004)

My diff growls when pulling from low revs... :runaway:

I have Nismo subframe & diff bushes. Mine doesn't clunk or knock though.


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## miragev (Apr 11, 2007)

Major_Sarcasm said:


> My diff growls when pulling from low revs... :runaway:
> 
> I have Nismo subframe & diff bushes. Mine doesn't clunk or knock though.


aren't the nismo one's rubber though..!! absorb the knocks and noise more

the polybush ones are really hard almost no give at all

like i said my diff didn't make noises until i fitted the polybushes


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## Major_Sarcasm (Jul 28, 2004)

The diff on my old 32 used to make a similar noise.

Probably just knackered


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## miragev (Apr 11, 2007)

Major_Sarcasm said:


> The diff on my old 32 used to make a similar noise.
> 
> Probably just knackered



you lost me now ...whats knackered yours or mine ?

mine didnt make noise until the bushes were fitted so it can't suddenly be knackered...


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## GOGS 2 (Jun 21, 2009)

when i change gear i sometimes hear a knocking noise from the back end. i was hoping it might of been the exhaust moving about. not the rear diff away to fall off


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## archaeic_bloke (Apr 22, 2008)

lol my god... read above guys... we just had this conversation... 

the solid subframe and diff spacer bushings make the differential noises more prevelant because it acts like an amplifier through the body of the car...

if you have nismo ones you won't hear this..

and no the box is not "knackered",,, it all works perfectly as it should.... its normal. as far as mine is concerned anyways....


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## n600hks (Aug 20, 2008)

well mine was like this no noise till i changed to poly and aluminium bushes clonk everytime i depress the clutch and release at the end changed the diff job done was nackered but makes it visible if bushes are changed altho the car drove spot on with the nackered one other then the clonk
if you do change the diff make sure you get new oil in it and enjoy it being on rails


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## archaeic_bloke (Apr 22, 2008)

if it drove "spot on" with the "nackered" one other than the clunk... then what exactly about the diff wasn't working right? lol....


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## Major_Sarcasm (Jul 28, 2004)

LOL, I didn't say anyone's was knackered except mine! My diff makes a growling noise, not a clunking.


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## archaeic_bloke (Apr 22, 2008)

ohhh!! lol... gotcha!


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## freakazoid3 (Jan 19, 2008)

Isn't it normal for a diff to make "a bit" of noise? Especially when still cold?
My front diff whines when cold eversince I changed the oil to a thicker equivalent but it goes away after 5min of driving...:nervous:


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## a2hox (Mar 20, 2008)

YES IT COMPLETELY NORMAL IF YOU HAVE AN AFTER MARKET DIFF


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## n600hks (Aug 20, 2008)

*diff*



archaeic_bloke said:


> if it drove "spot on" with the "nackered" one other than the clunk... then what exactly about the diff wasn't working right? lol....


altho the car behaves and drives normal it does irritate the clonking noise hence the change
by no means it will break down or cause any problems but then again ppl who love the car want the best out of it its like having a scar and getting surgery to remove it altho scar will make no difference


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## M SKinner (Feb 19, 2007)

Mine clonks too. You can also feel the lash in the driveline. I think its probably knackered diff bushes on mine. I'm planning to get a set of poly ones and see if that sorts it.


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## miragev (Apr 11, 2007)

M SKinner said:


> Mine clonks too. You can also feel the lash in the driveline. I think its probably knackered diff bushes on mine. I'm planning to get a set of poly ones and see if that sorts it.



NO....going by my experience it will just amplify the noise and get you even more worried ....like the car going to spontaneously explode at any moment...


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## M SKinner (Feb 19, 2007)

The amount of slack i can feel is WAY more than if it was just lash in the gears etc. So im gonna give bushes a go!


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## miragev (Apr 11, 2007)

found out why the diff was knocking 
the polybush rear subframe bushes are slightly shorter than the nissan bushes so it pulls the subframe closer to the mounts on the chassis maybe 2-3 mm this in turn presses the diff down on it's mounts and this causes the diff to knock on the lower diff cradle i just jacked up the diff slightly and slipped in a 3mm piece of rubber between the cradle and diff each side and now the knocking has gone and the back end is super tight ..and no noise..


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## mifn21 (Mar 19, 2007)

Wait til you try a Nismo diff - it knocks and bangs louder than a nympho with a megaphone :chuckle:


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