Unknown Issue causing shudder and vibration

[Robbo77]

TL,DR
shudder/vibration under car when it feels like it
Clunk when driving off at times
"Helicopter" sound from rear of car
Mechanic reckons no loose or obvious wear from inspection
Diff oil was low when he serviced it

Sorry for the long post guys just wanted to get as much info in as possible to try diagnose the issue.

So my 2014 VF SV6 Auto has something wrong which feels like it's coming from the rear end somewhere. Have had it serviced at the local mechanic and had him inspect for anything loose etc. And reckons he couldn't find anything.
Symptoms are a shuddering, vibration from under the car, can occur at seemingly any speed/acceleration, but not constant, car can be driving smoothly and then have a heavy shuddering which can be felt through the wheel and by passengers.
It has also been making a loud clunk from the rear end when taking off at standard/light acceleration, such as reversing out of a driveway and shifting to drive and pulling away. Again it doesn't do this every time.
Also I have noticed lately that I have been hearing what sounds almost like being pursued by a helicopter if that makes sense, kind of sound from the rear end, at first thought maybe an aircon sound but still present at times when it's off and just sitting in the car.
When serviced the Diff oil was very low.
After purchase found out previous owner was a bit of a hoon off road etc. Likely abused the poor thing.
Am I looking at likely a buggered diff.?
Or something drive shaft related..uni joint, centre bearing etc.
Transmission seems to shift smooth and fine so hoping it's all good. Worth a trans service?
Old mate says he doesnt want to start replacing things and looking for something that could be anything and tells me to go get the wheels balanced. However he also hasn't experienced the issue first hand. I'm very skeptical its a balance issue as I've experienced it now with 3 different sets of wheels/tyres on the car and don't wish to waste the cash on having balancing done should it turn out to be something expensive. Also the car drives smooth and at high speed other than when it has the obvious shudder so not thinking it's a wheel balancing issue.
Any help or suggestions would be much appreciated guys.
Cheers

 

[Aussie Trev]

I had a similar experience with a wagon I owned and tried everything including balancing the tail shaft all to no avail till eventually found it was the rear bearing in the gearbox. It seemed and sounded for all the world like shot unis most of the time and then other times there would be no noise or vibration. Drove me and my mechanic bananas.

 

[Forg]

Our VS had the occasional vibration above about 80km/h, stopping the car & looking for the cause would make it go away until it happened again maybe a few months later.

Nobody could find the cause, and it went away for good with new tyres - I always assumed one of the rear tyres or wheel-weights somehow caused it, but never really had proof.

So maybe a dodgy tyre? Have you tried using the spare as replacement for each of the fitted wheels, one corner at a time?

 

[Robbo77]

I had a similar experience with a wagon I owned and tried everything including balancing the tail shaft all to no avail till eventually found it was the rear bearing in the gearbox. It seemed and sounded for all the world like shot unis most of the time and then other times there would be no noise or vibration. Drove me and my mechanic bananas.

Yeah sounds like mine mate, it'll be fine 75% of the time until it decides it wants to do it, was that an affordable fix the rear bearing in the gearbox, as transmission problems go?

 

[Robbo77]

Our VS had the occasional vibration above about 80km/h, stopping the car & looking for the cause would make it go away until it happened again maybe a few months later.

Nobody could find the cause, and it went away for good with new tyres - I always assumed one of the rear tyres or wheel-weights somehow caused it, but never really had proof.

So maybe a dodgy tyre? Have you tried using the spare as replacement for each of the fitted wheels, one corner at a time?

Haven't tried that mate but have had 3 different sets of wheels each with different tyres on them on the car since I got it. Has had the shuddering vibration with all of them and at varying speeds/acceleration and other times just drives smoothly so it has to be something independent of the wheels I reckon.
Cheers for the reply

 

[Skylarking]

Mastering the terminology in describing a problem to the mechanic is the first step in solving any problem. Sadly such terminology is not defined in the owners manual so we need to get a copy of the workshop manual so as to learn to use the correct lingo.

Anyway, not sure what gearbox a 2014 SV6 has but a 'clunk' when going from reverse to drive is a known problem with 6L45 autos. It could be your 2014 sv6 auto has a similar issue. Your SV6 could also have a number of compounding problems making diagnosis somewhat difficult.

Anyway, check here for the 2015 6L45 shift clunk bulletin which describes the problem and the solution (i'm sure i've seen similar issue for 2014 VF's but a quick google didn't find the bulletin)....

Now if only Holden would release such bulletins via their web site, we could all gain a better understanding of the lingo and the common problems that impact our cars.

PS: edited to add that its a good idea to also run your hands over the rear tyre tread and feel for wavey or sawtooth pattern as that can sometimes cause weird vibration (bad bearing sound) at 30-40kmph even though the wheels are balanced and run OK at highway speeds.

 

[Aussie Trev]

Yeah sounds like mine mate, it'll be fine 75% of the time until it decides it wants to do it, was that an affordable fix the rear bearing in the gearbox, as transmission problems go?

From memory, it was quite a few years back, it was pretty simple removing the rear extension and replacing the bearing without having to take the box out. Talking about a VN in my case so can't say if yours would be similar. I wasn't there when the mechanic did it so don't know exactly what the process was.

 

[RiCeY]

Sounds like centre bearing, you need to drop exhaust and heat shield to inspect it.

 

[Cuz_brah]

Not sure if our issues are the same and hopefully yours is fixed by now. When I had that shudder car wide, took it to the dealer and they said it was the torque converter that was cooked. Shaking would kick it around 1250-1500rpm. Could it be same thing? maybe maybe not?

 

[Filthy 1]

Hi Robbo, my wife has same issue with her 2014 VF Calais, intermittent shuddering. Just wondering if you ended up resolving the issue? I'm thinking maybe driveshaft universal but noted online that GMH had an issue with VE torque convertors in 2012. Regards, Phil