knocking noise on take off only

[tenggo]

Hi there i have a vr acclaim and lately i have been getting a knocking noise on take off. it sounds like it is coming from where a persons feet would be if they were sitting in the middle back seat... it only happens in the first 5 meters of take off from a complete stop. Never happens while driving, and gear changes and engine run sweet. any help appreciated, cheers.

[moff_man]

the only thing in that area is a tail shaft and a handbrake cable, might want to pop under neath and have a look maybe the centre bering has come loose

[H1GHROLLR]

maybe your flex plate

[tenggo]

i will have a look under it tomorrow to see if i can spot anything loose... a bit more info, if i take off slowly it doesnt happen, if i give it a bit it will make the noise, it only lasts for a second or 2 but just worried if left unchecked it could turn into something worse...

[Dyson]

My VS makes the same sound, only it does it when I brake/stop aswell.

[hako]

As moff_man suggests it certainly sounds like the centre bearing has failed. Check by crawling under the car (safely!) and grasp the prop shaft halfway between the back of the transmission and the diff and see if it moves side to side.....it should be pretty firm.

[tenggo]

Hey there, got under the car and tried to wiggle the tail shaft, it is solid with no obvious wobble. Buggered if i know what it is, only happens on take off for about a car length and only if take off normally, if i take off like an old lady it doesnt happen... any suggestions

[RMXR]

Engine mount???

My VS developed a heavy knock under acceleration from low speed. Left hand engine mount was totally stuffed.

[DannyboyDS]

my car does this too, both engine mouns and the trans mount got replaced last year, visual inspection and jimmy bar test all pass for the mounts, im tipping towards the tailshaft as well, you can normally pick a second hand one up for $50 from the wreckers, give it a go I know i'm going to.

[tenggo]

Will a vs non irs tail shaft fit into a vr irs? i have a vs i am wrecking and the shaft is fine so can i put that into the vr? cheers

[VT-565]

It is most likely the centre bearing.

Changing the tailshaft with one from the wreckers could only buy you someone else's rooted centre bearing lol

Replace it and see if it still does it.

[VrWagz1]

If you have extractors, its not them rubbing under the floor cause of a failed engine mount maybe?

[VT-565]

it sounds like it is coming from where a persons feet would be if they were sitting in the middle back seat...

If you have extractors, its not them rubbing under the floor cause of a failed engine mount maybe?

Long primaries lol.

I'm still convinced its the centre bearing, if it was a failed engine mount, vehicle speed would be irrelevant, but engine load would be the dictator of when it knocks on the floor.

[DannyboyDS]

with engine mounts though a sudden change in load could cause a knock.

To the OP yes you may be buying someone elses rooted center bearing, then again more then likely not, just gotta pick a winner I guess, What are they worth brand new again?

[VT-565]

with engine mounts though a sudden change in load could cause a knock.?

I'm still convinced its the centre bearing, if it was a failed engine mount, vehicle speed would be irrelevant, but engine load would be the dictator of when it knocks on the floor.

Good to see you're thinking on your own.

To the OP yes you may be buying someone elses rooted center bearing, then again more then likely not, just gotta pick a winner I guess, What are they worth brand new again?

Not just the centre bearing, but small dents in the driveshaft can cause an imbalance and you won't know until you put it on the car and drive off.

Anyway, found new centre bearings on ebay for less than $30.

[DannyboyDS]

hey got a link for them on ebay, I may as well get a new one too since I have the same issue.

I didn't realise I said the same thing as you but a bit differently, however I think you will see across the whole forums people often end up having the same ideas or thoughts especially if it is tipping towards being correct.

I remember when I had issues with my engine mounts I could get it to "knock" if I suddenly pushed my foot on the accelorator from any speed or if I was stationary from neutral to drive was ok, but when I went neutral to reverse the revs would pick up a bit during the change and "clunk" from the engine bay as it went in, thats how I noticed it.

ended up having to do both engine mounts, was a fun way to waste an afternoon.

[VT-565]

jump on ebay and search for "vr commodore centre bearing"

that's all i did and came up with a heap.

[tenggo]

Thanks for the advice, will fix the center bearing and see if that fixes it, i have a donor car with a good tail shaft, would it be easier to just change the whole thing or just the bearing. the donor car is non irs vs and the good car is irs vr are these interchangable? Are there any tricky bits or is it a bolt off bolt on type of deal, cheers