Driveline vibration. Need help.

[nigelmelb]

HI there.
I have searched through many threads on the issue and followed advice with no luck.
I have a WH series 2 LS1 with a fairly bad driveline vibration. Long story short, I had to replace the centre bearing and we were not able to separate the shaft to do this. We even sent it off to a tail shaft specialist and they could not separate it either. I had to source a second hand tail shaft so we could separate it and put a new centre bearing on. Since installing it the car has had a pretty severe tail shaft vibration.
I have had it balanced twice buy a tail shaft guy with no luck. We had it balanced a third time with a tail shaft specialist in Melbourne with a very reputable name also with no luck. Each time the vibration changes. It varies to different speeds after each balance.
I am running out of ideas. The doughnuts are in good condition. My mechanic who builds well-known drag cars and knows this area well is puzzled by the problem. It is not easy to find another shaft so can't find another one to try. If the tail shaft specialist say it is fine then in theory it is not the tail shaft. Next step is to replace engine and transmission mounts as well as maybe the diff mount. They are all apparently in good condition so not sure if it will be a waste of money.
My thoughts are it must be the tail shaft as the car was perfect with the original tail shaft even though the centre bearing rubber was gone and all we did was changed the shaft. That's when the problem started. Just doesn't make sense that if it has been balance three times and the last being I very highly rated expert then it should be perfect of they say it is.
Any ideas guys? Maybe the trans and engine mounts have gone hard as they are original? Still doesn't make sense that this problem only started after we source a second tail shaft.
Thanks.

 

[Not_An_Abba_Fan]

When doing a centre bearing you need to mark each component as you take it apart so that it bolts back together in exactly the same way. If you don't get it back together the same as it came apart, it vibrates. To fix it, the couplings have to be phased correctly, then the whole unit balanced.

 

[nigelmelb]

When doing a centre bearing you need to mark each component as you take it apart so that it bolts back together in exactly the same way. If you don't get it back together the same as it came apart, it vibrates. To fix it, the couplings have to be phased correctly, then the whole unit balanced.

Thanks mate. Not sure if this happened or not but the whole shaft has now been balanced and they say its fine. Doesn't make sense.

 

[vc commodore]

Thanks mate. Not sure if this happened or not but the whole shaft has now been balanced and they say its fine. Doesn't make sense.

I'm not doubting the specialists you have been through, but you have already pointed to what the problem is....Your current tailshaft...You have already admitted the vibration wasn't there before you changed tailshafts, now it is....

If you still have your old tailshaft, put it in and see if the vibration disappears...This will confirm or deny the problem exists with your currrent tailshaft, therefore being able act accordingly

 

[nigelmelb]

I don't have the original any more. It was damaged trying to split it in two.
Yeah I totally agree but it just doesn't make sense. If the shaft specialist is saying its balanced perfect better than from factory then it should be perfect.
I'm trying to look for another but they aren't easy to find.

 

[Trevor loves holden.]

Have you tried moving the shaft at the diff and turn it one bolt hole at a time do it back up and see if it goes away.

 

[rambunctious]

You may be experiencing harmonic vibration meaning something in the car is out of harmony with something else.

Replace the engine mounts and gearbox mount, as these vehicles are very touchy when it comes to mounts, and most importantly, use genuine from Holden, not genuine from Repco, not genuine from Burson or Superthief, must be genuine from Holden.

I had a 5 litre many years ago and the imbicile mechanic fitted nolathene mounts then he tried rubber mounts from Repco but still no good and the car nearly shook itself to death until I replaced the mounts with genuine from Holden.

I spent a fortune on tailshaft balancing at the time with no success.

I think you get my drift, the mounts must be genuine from Holden.

 

[Not_An_Abba_Fan]

Most of the time a shaft will balance up perfectly on the machine, but because the mounts on either end are out of phase it will vibrate on the car. Usually you will feel a cyclic vibration.

 

[Pollushon]

I'd check the trans-mount. When I did the same as you some time ago on a VY SS I found the tight new driveshaft tipped it over the edge. I only saw vibration on heavy acceleration but the new trans mount sorted it.

 

[rambunctious]

Most of the time a shaft will balance up perfectly on the machine, but because the mounts on either end are out of phase it will vibrate on the car. Usually you will feel a cyclic vibration.

That's what I meant by harmonic.