Knocking Sound

[chrism182]

Recently a sound has been coming from the back end of my VX Commodore. It has been coming and going lately and it's come back today so I've decided to try and do something about it It only happens when I accelerate.

We think it's the diff, dad reckons that sometimes if the diff has the wrong oil it could do this, but the diff oil got changed 10,000km's ago.

Any help would be much appreciated.

Cheres,
Chris.

[Sabbath']

Could be your diff, tailshaft, cv joints....

[vt s]

Probably just the usual drivetrain slop the commodores develop.

[chrism182]

Hmm.. And what are we looking at to fix it?

[accentstencil]

Do you have a limited slip diff? I recently developed a knock from the diff, mainly when turning right. I changed the diff oil and added the additive that goes with it and the noise disappeared after about a day.
Did you put the additive in when you changed the oil?

[chrism182]

Do you have a limited slip diff? I recently developed a knock from the diff, mainly when turning right. I changed the diff oil and added the additive that goes with it and the noise disappeared after about a day.
Did you put the additive in when you changed the oil?

Yeah it is an LSD. Nope didn't put the oil in myself got the local Tyrepower to do it during the service when I first bought it. Not sure if they put the additive in.

Cheers.

[vt s]

If it is just drivetrain slack i wuldnt be worried about it.
For the money its gona cost to get rid of it just not worth it.
Accidencil youl probably find after few days, weeks or months your knocking sound will probably come back.
The fresh oil and additive will cure it for a while but its probably gonna need a rebuild later on.
Not that i would be worried as mine knocks like crazy lol.

[accentstencil]

Yeah it is an LSD. Nope didn't put the oil in myself got the local Tyrepower to do it during the service when I first bought it. Not sure if they put the additive in.

Cheers.

You might want to check to see if they put the anti friction additive in as it is apparently quite important.

[chrism182]

If it is just drivetrain slack i wuldnt be worried about it.
For the money its gona cost to get rid of it just not worth it.
Accidencil youl probably find after few days, weeks or months your knocking sound will probably come back.
The fresh oil and additive will cure it for a while but its probably gonna need a rebuild later on.
Not that i would be worried as mine knocks like crazy lol.

It's not just a small knock, it's quite loud which is why I'm worried about it.


What diff oil would you recommend? And what is the additive?

[accentstencil]

It's not just a small knock, it's quite loud which is why I'm worried about it.


What diff oil would you recommend? And what is the additive?

I went to a place that repairs diffs and bought the oil and additive from them.
Is it a single knock or several knocks in succession and does it happen when going straight or when going slowly around a bend?

[chrism182]

It's several knocks every time I accelerate, both straight and going around a bend.

Doesn't happen when I take my foot of the accelerator.

[accentstencil]

It's several knocks every time I accelerate, both straight and going around a bend.

Doesn't happen when I take my foot of the accelerator.

It sounds similar to the problem I had and I hear it happens a fair bit and the additive can fix it but for how long, I don't know. The oil I drained from my diff was very old and disgusting.

[vt s]

If it is several knocks in succesion then sounds like its inside the diff.
As accentstecil suggested change the oil in it and see how it goes.
Holden use 80-140 from factory with their own additive, the name i cant remember anymore lol.
Anything in that grade should be fine alot people use different oils ive found castrol SAF-XA to be the most popluar as it has the additive all ready mixed with it so makes it a bit easier.
I myself just use valvoline 75-140 with a valvoline additive seems to work fine.
Looking to try the castrol next time, by then im sure the diffs def gona need a rebuild lol.
Diff oil seems to be one area highly overlooked during servicing maybe thats why they dont last long...

[vt s]

Do you know whether it does it in reverse?
And it definately doesnt do it when foot off accelerator still going slow?

[chrism182]

Do you know whether it does it in reverse?
And it definately doesnt do it when foot off accelerator still going slow?

Not sure if it does it in reverse..

and yeah it doesn't do it when the foot is off the accelerator going slow, pretty sure anyway.

It's due for a service anyway so I'll take it to my mechanic later on this week and he can check it out.

[VRSen]

IMHO i reckon its your pinion bearing to be honest had the same thing with my patrol.

[curtcommy]

same happens here. sound coming from rear right side. occurs when foot put down, genrelly a doule thud thud

[accentstencil]

Update: the knocking has returned in my diff after about a week. Some-one recommended a Nulon friction modifier that worked for them after several other brands did not fix the problem. I will try it and report back.

[vt s]

Its hard to pinpoint exactly most of the time.
It could also be the CV's.
Most people dont find this out until they spend over a grand getting the diff rebuilt.

[chrism182]

According to my mechanic it is my CV joint. I'll be replacing it soon and I'll report on how it went.

[VL-VP-VT]

hey guys, sorry to bring an old thread back to life, but this thread is the closest to the problem I am having at the moment, I recently bought a WHII Statesman it's a GENIII with an LSD not sure of the ratio, but don't think that matters. any way I have the thuds that have been mentioned in this thread and was wondering if anyone has a solution yet, as i've read the diff should have an additive in, as i've just bought this car I don't know if it has been added or not. anyway I usually get 2-5 thuds on light accelleration but only from a stopped position eg. (only after stopping at an intersection, or pedestrian crossing) or driving off after the car has been sitting, and it DOES happen in reverse (when reversing out driveway) the car has a 12 month warranty on it which covers the DIFF's Internals.. which is why I want to get to the bottom of it, also if I accelerate a bitter harder from a stopped position I get 1 thud (or more a clunk) is this just an LSD Clunk or should I be concerned about it, I've had the car up on a hoist and checked as many things that could thud, but can't seem to find anything loose or worn in the back end, originally thinking other than the diff I thought the brakes may have been grabbing slightly, so backed the handbrake right off and replaced the rear pads with Bendix. but still does it. only other problem I could find was slight sideways movement in the CV's but I don't think this is the issue..
I took the car to pedders for their $14 - 28 point safety check, but he couldn't get the car to replicate the thuds. he picked up on the strut bar to chassis bushes and said they'd need replacing (I did that but that was definately not where it is coming from)
any help is greatly appreciated.