Common vy diff fault

[VYMAD]

Hey i saw on here ages ago that the fault with the vy diffs, you know the "clunk" when backing off and then accellerating again was initially diagnosed by Holden as requireing a "complete diff rebuild" costing around a grand. Apparently it's actually just a couple of curclips or something and an hour or two labour. Anyone had there's fixed that could tell me how they went with it and how much etc. Might ask Holden, "You know the common vy diff fault......" and see what they say. Thanks.

[SAV_117]

mine does that i was hoping i was hearing things lol

[VYMAD]

Yeah at first i thought was uni-joint but no such luck!!! Saw on this site somewhere ages ago a whole heap of posts about it but can't seem to be able to find them now, anyone know?

[Sebastien]

i can faintly hear it, only because i listen out for it because i'm pedantic..

I'm not worried though whenever it decides to let go it'll be a good reason to throw in an LSD.


Speaking of which does anyone know how i can work out if its LSD or not without jumping on the anchors and giving the go pedal a boot?

[jack09]

whoa i get this too, kinda glad to hear it's not just my car i think??

so what can happen if its not fixed and how much to fix it?

[VYMAD]

Come on someone must remember all the posts up here about the issue I can't seem to find anything on here now. Wasn't it a problem with VX/VY?

[fleet5ltr]

Diff noise " cyclic knock " a Holden Service Issues

I think this is the one

[VYMAD]

Thank you fleet5ltr, I spent an hour or so this afternoon reading through the entire "issues with vy's" thread but only a couple of minor mentions on the issue. So I wonder where I can find a mechanic that'll be aware of the fault and able to fix it (other than holden)!!!!!!?

[greggold]

Thanks to Georgehifi and Vymad for this explanation of the differential thump noise. I too have been told by a holden dealer that the only solution is a $1000 diff rebuild. I was told it is "differential backlash" which may be a fictional condition, ie it does not exist. It seems GM in their 2005 memo identified the issue as "rear axle cyclic knock" and posted a solution in the technical memo that Georgehifi posted. A recall of all cars built with the fault was not done.

It does look very ugly indeed. I have had a relationship with my holden dealer for years, now I doubt I can trust them.

I would appreciate any practical suggestion as to how I might solve my problem. Advice from anyone who has solved this issue would be particularly appreciated.

[TMM]

Every VT-VZ i've been in does this to some degree. It's most noticable when rolling along at about 20km/h, then you floor it and get the clunk. It's not really anything to worry about. I know someone who went through 3 or 4 diffs under warranty to get rid of it, lol.

[danja]

I don't think your problem is the same as the cyclic knock problem.

Cyclic knock is described as occuring as the vehicle decellerates from a moderate speed, without being under load. Eg, you accellerate to 70, then coast down to 20.

If I'm not mistaken the problem you're having is that when you apply power, or remove power suddenly, there is a "clunk" or "knock" from the diff? That's happened in every Commodore I've ever driven. I believe it's caused by play in the driveline, due to worn driveline mounts/bushes.

I don't have any reason to think it's detrimental, whereas it seems if you leave the cyclic knock untreated you'll eventually destroy your diff and/or driveshafts.

[greggold]

I agree with Danja that my noise seems more like differential backlash than rear axle cyclic knock. My Holden dealer called it diff backlash, and said not to worry about it. But the problem is the noise is not a single knock, it is a cyclic noise that changes frequency as you accelerate, and disappears by the time you reach 60 km. The problem is, in slow traffic, it becomes a real pain, and requires to be fixed.
I am planning to take it to a specialist differential/axle service centre in Sydney, seeing as how my dealer now doesn't want to know about the problem. (I am less critical of my dealer than I was, as I now think his diagnosis is likely correct, but he still scores 0/10 for performance in paying attention to the customers concerns, especially as I have asked him on 3 occasions to fix it; and can he really not have a clue about how to fix it?).

Has anyone ever heard of a case of differential backlash being fixed? Is complete replacement of the diff the only solution?

[VYMAD]

Hey Greggold if you have any luck from the specialist can you PLEASE post what the outcome was? Would be awesome to find if the problem is actually "easily" fixed with those couple of curclips.

[greggold]

There are 2 threads going under vy commodore on this topic the other is "diff clunk question"

As I just posted on the other thread

The noise in my differential described in my previous post may either be differential backlash or cyclic rear axle knock; I have talked about this with various people including a mechanical engineer and it is not clear which is the more likely. So I have decided to get a differential and axle specialist service shop to have a go at repair, I am booked in 12 May. I have been warned it will likely cost $900.

Yes I will do a post about the result

[VYFORI]

Gday peoples would a Nothalane crossmember mount reduce this problem

Redranger Nolathane for longer life suspension systems

RIK...

[vtclubby195i]

could b diff chatter?mite jus need a flush an oil change.had the same problem in my vt clubby flushed diff an put 80w/140lsd synthetic oil in an it went away.

[jet-6]

Oil type will make a huge difference, i ran "redline" full synth in my Nissan diff and the noises coming from it were insane(mind you it was like liquid locker), swapped back to Penrite 140 and its like it new now!

[VYMAD]

How do you flush it?

[greggold]

Hey Greggold if you have any luck from the specialist can you PLEASE post what the outcome was? Would be awesome to find if the problem is actually "easily" fixed with those couple of curclips.

I had my car repaired today. The noise was present when I took the car in, so it was easy to demonstrate to the mechanic. The problem was initially not obvious, but I was later phoned and told they found damage to the left CV shaft ("constant velocity" shaft joining the differential and axel that has some complex gearing at each end).
The left side cv shaft was replaced and the problem now seems solved, although so far I have only driven the car for one hour (but it was in traffic at low speed, when my noise had previously been obvious). The cost was $350 for the new cv shaft and $90 labour, total $440.
I had been quoted around $1000, or more if parts were needed, but that was over the phone when my understanding was that it was the differential at fault.

I think it is likely the car really is fixed, and I cant speak too highly of the shop - its Hornsby Differential and Gearbox. I cant recall a previous instance of car repair in my experience where the final price was so much lower than what was quoted. Adam said the cv shaft problem is not so common.

My Holden dealer had been asked to fix the noise on 3 occasions, and 3 times I was told dont worry about it, its was a normal noise.

[danja]

I had my car repaired today. The noise was present when I took the car in, so it was easy to demonstrate to the mechanic. The problem was initially not obvious, but I was later phoned and told they found damage to the left CV shaft ("constant velocity" shaft joining the differential and axel that has some complex gearing at each end).
The left side cv shaft was replaced and the problem now seems solved, although so far I have only driven the car for one hour (but it was in traffic at low speed, when my noise had previously been obvious). The cost was $350 for the new cv shaft and $90 labour, total $440.
I had been quoted around $1000, or more if parts were needed, but that was over the phone when my understanding was that it was the differential at fault.

I think it is likely the car really is fixed, and I cant speak too highly of the shop - its Hornsby Differential and Gearbox. I cant recall a previous instance of car repair in my experience where the final price was so much lower than what was quoted. Adam said the cv shaft problem is not so common.

My Holden dealer had been asked to fix the noise on 3 occasions, and 3 times I was told dont worry about it, its was a normal noise.

Good news. Hope the problem is well and truly solved for you now.

Reminds me of a similar thing which happened to me. I parked my car one night, went out for dinner, then got back to the car, drove out the parking lot and up to some lights. Lights went green and as I turned the corner a horrible sound came from under the car, like I'd run over tumbleweed made of barbed wire and was dragging it under the car, along with various clunks and bad vibrations. I immediately suspected the diff had shat itself, and got the car towed to my local mechanic.

Next morning I asked the mech to take a look at it, and described the problem. They agreed it was probably the diff, and could cost anywhere between $1000-1500 to fix. I said "yeah, well thats pretty much what I was expecting", and left it with them. Later that day got a call "good news, you just tore a half-shaft - $200 inc labor"

[VYMAD]

Ok ta, I might have a chat to a few mechanics in Bundy and see what they reckon, at least now there's a possible cause.

[Calaber]

I agree with Danja that my noise seems more like differential backlash than rear axle cyclic knock. My Holden dealer called it diff backlash, and said not to worry about it. But the problem is the noise is not a single knock, it is a cyclic noise that changes frequency as you accelerate, and disappears by the time you reach 60 km. The problem is, in slow traffic, it becomes a real pain, and requires to be fixed.
I am planning to take it to a specialist differential/axle service centre in Sydney, seeing as how my dealer now doesn't want to know about the problem. (I am less critical of my dealer than I was, as I now think his diagnosis is likely correct, but he still scores 0/10 for performance in paying attention to the customers concerns, especially as I have asked him on 3 occasions to fix it; and can he really not have a clue about how to fix it?).

Has anyone ever heard of a case of differential backlash being fixed? Is complete replacement of the diff the only solution?

Diff backlash can be caused by a couple of things.

The first is the freeplay between the pinion gear and crownwheel. It is adjusted by means of shims and torque on the retaining nut on the pinion. The clunk you would hear on accelleration or decelleration is caused by the two gears taking up the slack - it might only be a millimetre or so between the gears but is sufficient to permit a perciptible clunk when the gears engage. Unless the freeplay is excessive, it is not really a problem.

The second is the wear that occurs on the splines at the end of the axles in the planetary side gears. This is where the circlips are located. If the lash is excessive between the axle and gear, you can get a clunk there but it is not normally as noticeable as pinion lash. Looking through the manual, I can't see any other circips in the diff assembly so I have to assume it is those two that are the subject of the tech notes.

.

[VYMAD]

Diff backlash can be caused by a couple of things.

The first is the freeplay between the pinion gear and crownwheel. It is adjusted by means of shims and torque on the retaining nut on the pinion. The clunk you would hear on accelleration or decelleration is caused by the two gears taking up the slack - it might only be a millimetre or so between the gears but is sufficient to permit a perciptible clunk when the gears engage. Unless the freeplay is excessive, it is not really a problem.

The second is the wear that occurs on the splines at the end of the axles in the planetary side gears. This is where the circlips are located. If the lash is excessive between the axle and gear, you can get a clunk there but it is not normally as noticeable as pinion lash. Looking through the manual, I can't see any other circips in the diff assembly so I have to assume it is those two that are the subject of the tech notes.

.

I think my only option would be to find a reputable mechanic and get him to come drivies with me to hear the clunk, or thud which is probably a better description, and let him have a go at it. Might wait until if/when the sound gets worse though as if it's so common with these diffs and they're not all blowing up all the time then it may not be too much of a concern.

[Calaber]

I think my only option would be to find a reputable mechanic and get him to come drivies with me to hear the clunk, or thud which is probably a better description, and let him have a go at it. Might wait until if/when the sound gets worse though as if it's so common with these diffs and they're not all blowing up all the time then it may not be too much of a concern.

I think I'd get a differential specialist to assess it. Check Yellow Pages under "Transmissions - Automotive-Car" to see if there is one near you.

[danja]

It's also common for the differential mount to wear out, leading to excessive play in the drive line. This can give a "clunk" similar to driveline lash. As Calaber suggests, get a specialist to look at it - a regular mechanic is less likely to be able to accurately determine the cause.